Prime Minister David Cameron said on Thursday Britain will be "toughening" up its response to Russia after a public inquiry implicated President Vladimir Putin in the assassination of Alexander Litvinenko.
The Tory leader stopped short of threatening to end ties with Russia, noting the UK must have "some sort" of relationship with Moscow.
However, Cameron promised future dealings with Russia would be carried out with "clear eyes and a very cold heart" after the publication of Sir Robert Owen's report that concluded Putin "probably" signed off the fatal poisoning of Litvinenko, who died from ingesting radioactive polonium in London in 2006.
Marina Litvinenko speaks outside The High Court after publication of the inquiry into the death of her husband Alexander Litvinenko, on January 21, 2016 in London, England
Speaking in Davos, Cameron called the state-sponsored murder "absolutely appalling," adding that the report confirms what "we have always believed.”
In response, Maria Zakharova, a spokeswoman for the Russian foreign ministry, said: “We regret that a purely criminal case has been politicised and has darkened the general atmosphere of our bilateral relations.”
“Taking this into account, there were little grounds to expect that the final report of a process that was politically motivated and highly opaque, and prepared with a pre-determined ‘correct’ result in mind, would suddenly turn out to be objective and balanced,” she added.
Litvinenko Inquiry
Litvinenko inquiry findings(01 of37)
Marina Litvinenko, the wife of former Russian spy Alexander Litvinenko, with her son Anatoly during a press conference at the Griffin Building, Gray's Inn, London, after the findings of the inquiry into his death were revealed. (credit:Philip Toscano/PA Wire)
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Marina Litvinenko, widow of ex-Russian spy Alexander Litvinenko, holds up the report into the death of her husband at a press conference in London on Janurary 21, 2016. Russian President Vladimir Putin 'probably approved' the radiation poisoning of former KGB agent Alexander Litvinenko in London, a British judge said at the conclusion of a public inquiry into his agonising death. Litvinenko was allegedly poisoned at a hotel by a cup of tea laced with polonium-210 -- an extremely expensive radioactive isotope only available in closed nuclear facilities -- in a sequence of events which could have come from a Cold War thriller.AFP PHOTO / JUSTIN TALLIS / AFP / JUSTIN TALLIS (Photo credit should read JUSTIN TALLIS/AFP/Getty Images) (credit:JUSTIN TALLIS via Getty Images)
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Marina Litvinenko (R), widow of ex-Russian spy Alexander Litvinenko poses with her son Anatoly after a press conference in London on Janurary 21, 2016. Russian President Vladimir Putin 'probably approved' the radiation poisoning of former KGB agent Alexander Litvinenko in London, a British judge said at the conclusion of a public inquiry into his agonising death. Litvinenko was allegedly poisoned at a hotel by a cup of tea laced with polonium-210 -- an extremely expensive radioactive isotope only available in closed nuclear facilities -- in a sequence of events which could have come from a Cold War thriller.AFP PHOTO / JUSTIN TALLIS / AFP / JUSTIN TALLIS (Photo credit should read JUSTIN TALLIS/AFP/Getty Images) (credit:JUSTIN TALLIS via Getty Images)
Results Of The Inquiry Into The Death Of Alexander Litvinenko Are Published(04 of37)
LONDON, ENGLAND - JANUARY 21: Marina Litvinenko holds a copy of the inquiry report as she attends a press conference at her lawyer's office after receiving the results of the inquiry into the death of her husband Alexander Litvinenko, on January 21, 2016 in London, England. Former KGB officer Alexander Litvinenko was poisoned in 2006 with radioactive polonium-210 in the United Kingdom having fled Russia after criticising president Vladimir Putin. (Photo by Carl Court/Getty Images) (credit:Carl Court via Getty Images)
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Marina Litvinenko, widow of ex-Russian spy Alexander Litvinenko takes part in a press conference in London on Janurary 21, 2016 following the publication of the public inquiry into the death of her husband. Russian President Vladimir Putin 'probably approved' the radiation poisoning of former KGB agent Alexander Litvinenko in London, a British judge said at the conclusion of a public inquiry into his agonising death. Litvinenko was allegedly poisoned at a hotel by a cup of tea laced with polonium-210 -- an extremely expensive radioactive isotope only available in closed nuclear facilities -- in a sequence of events which could have come from a Cold War thriller.AFP PHOTO / JUSTIN TALLIS / AFP / JUSTIN TALLIS (Photo credit should read JUSTIN TALLIS/AFP/Getty Images) (credit:JUSTIN TALLIS via Getty Images)
Results Of The Inquiry Into The Death Of Alexander Litvinenko Are Published(06 of37)
LONDON, ENGLAND - JANUARY 21: Marina Litvinenko (R) and her son Anatoly attend a press conference at their lawyer's office after receiving the results of the inquiry into the death of Marina's husband Alexander Litvinenko, on January 21, 2016 in London, England. Former KGB officer Alexander Litvinenko was poisoned in 2006 with radioactive polonium-210 in the United Kingdom having fled Russia after criticising president Vladimir Putin. (Photo by Carl Court/Getty Images) (credit:Carl Court via Getty Images)
Results Of The Inquiry Into The Death Of Alexander Litvinenko Are Published(07 of37)
LONDON, ENGLAND - JANUARY 21: Marina Litvinenko (C) and her son Anatoly (3rdL) attend a press conference at their lawyer's office after receiving the results of the inquiry into the death of Marina's husband Alexander Litvinenko, on January 21, 2016 in London, England. Former KGB officer Alexander Litvinenko was poisoned in 2006 with radioactive polonium-210 in the United Kingdom having fled Russia after criticising president Vladimir Putin. (Photo by Carl Court/Getty Images) (credit:Carl Court via Getty Images)
Results Of The Inquiry Into The Death Of Alexander Litvinenko Are Published(08 of37)
LONDON, ENGLAND - JANUARY 21: Marina Litvinenko holds a copy of the inquiry report as she attends a press conference at her lawyer's office after receiving the results of the inquiry into the death of her husband Alexander Litvinenko, on January 21, 2016 in London, England. Former KGB officer Alexander Litvinenko was poisoned in 2006 with radioactive polonium-210 in the United Kingdom having fled Russia after criticising president Vladimir Putin. (Photo by Carl Court/Getty Images) (credit:Carl Court via Getty Images)
Results Of The Inquiry Into The Death Of Alexander Litvinenko Are Published(09 of37)
LONDON, ENGLAND - JANUARY 21: Marina Litvinenko (R) and her son Anatoly attend a press conference at their lawyer's office after receiving the results of the inquiry into the death of Marina's husband Alexander Litvinenko, on January 21, 2016 in London, England. Former KGB officer Alexander Litvinenko was poisoned in 2006 with radioactive polonium-210 in the United Kingdom having fled Russia after criticising president Vladimir Putin. (Photo by Carl Court/Getty Images) (credit:Carl Court via Getty Images)
Results Of The Inquiry Into The Death Of Alexander Litvinenko Are Published(10 of37)
LONDON, ENGLAND - JANUARY 21: Marina Litvinenko (C) and her son Anatoly (L) listen as their lawyer, Ben Emmerson, speaks during a press conference after receiving the results of the inquiry into the death of Marina's husband Alexander Litvinenko, on January 21, 2016 in London, England. Former KGB officer Alexander Litvinenko was poisoned in 2006 with radioactive polonium-210 in the United Kingdom having fled Russia after criticising president Vladimir Putin. (Photo by Carl Court/Getty Images) (credit:Carl Court via Getty Images)
Britain Poisoned Spy(11 of37)
Marina Litvinenko, widow of former Russian spy Alexander Litvinenko, arrives for a press conference in London, Thursday, Jan. 21, 2016. Judge Robert Owen said Thursday he is certain that Litvinenko was given tea laced with a fatal dose of polonium-210 at a London hotel in November 2006. He says there is a "strong probability" that the FSB directed the killing and the operation was "probably approved" by Russian President Vladimir Putin. (AP Photo/Matt Dunham) (credit:ASSOCIATED PRESS)
Britain Poisoned Spy(12 of37)
Marina Litvinenko, widow of former Russian spy Alexander Litvinenko, speaks during a press conference in London, Thursday, Jan. 21, 2016. Judge Robert Owen said Thursday he is certain that Litvinenko was given tea laced with a fatal dose of polonium-210 at a London hotel in November 2006. He says there is a "strong probability" that the FSB directed the killing and the operation was "probably approved" by Russian President Vladimir Putin. (AP Photo/Matt Dunham) (credit:ASSOCIATED PRESS)
Britain Poisoned Spy(13 of37)
Marina Litvinenko, widow of former Russian spy Alexander Litvinenko, speaks during a press conference in London, Thursday, Jan. 21, 2016. Judge Robert Owen said Thursday he is certain that Litvinenko was given tea laced with a fatal dose of polonium-210 at a London hotel in November 2006. He says there is a "strong probability" that the FSB directed the killing and the operation was "probably approved" by Russian President Vladimir Putin. (AP Photo/Matt Dunham) (credit:ASSOCIATED PRESS)
APTOPIX Britain Poisoned Spy(14 of37)
Marina Litvinenko, widow of former Russian spy Alexander Litvinenko, places her arm around her son Anatoly during a press conference in London, Thursday, Jan. 21, 2016. Judge Robert Owen said Thursday he is certain that Litvinenko was given tea laced with a fatal dose of polonium-210 at a London hotel in November 2006. He says there is a "strong probability" that the FSB directed the killing and the operation was "probably approved" by Russian President Vladimir Putin. (AP Photo/Matt Dunham) (credit:ASSOCIATED PRESS)
BRITAIN-RUSSIA-POLITICS-SPY(15 of37)
Marina Litvinenko (C), widow of Russian former spy Alexander Litvinenko, and her son Anatoly Litvinenko (R), arrive at the Royal Courts of Justice in central London on Janurary 21, 2016. A British judge could point the finger at Russia for the radiation poisoning of former KGB agent Alexander Litvinenko in London as an inquiry into his agonising death publishes its conclusions. Litvinenko was allegedly poisoned at a hotel by a cup of tea laced with polonium-210 -- an extremely expensive radioactive isotope only available in closed nuclear facilities -- in a sequence of events which could have come from a Cold War thriller. AFP PHOTO / JUSTIN TALLIS / AFP / JUSTIN TALLIS (Photo credit should read JUSTIN TALLIS/AFP/Getty Images) (credit:JUSTIN TALLIS via Getty Images)
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Marina Litvinenko (L), widow of Russian former spy Alexander Litvinenko, and her son Anatoly Litvinenko, arrive at the Royal Courts of Justice in central London on Janurary 21, 2016. A British judge could point the finger at Russia for the radiation poisoning of former KGB agent Alexander Litvinenko in London as an inquiry into his agonising death publishes its conclusions. Litvinenko was allegedly poisoned at a hotel by a cup of tea laced with polonium-210 -- an extremely expensive radioactive isotope only available in closed nuclear facilities -- in a sequence of events which could have come from a Cold War thriller. AFP PHOTO / JUSTIN TALLIS / AFP / JUSTIN TALLIS (Photo credit should read JUSTIN TALLIS/AFP/Getty Images) (credit:JUSTIN TALLIS via Getty Images)
Results Of The Inquiry Into The Death Of Alexander Litvinenko Are Published(17 of37)
LONDON, ENGLAND - JANUARY 21: Marina Litvinenko (c) and son Anatoly Litvinenko arrive at The High Court to receive the results of the inquiry into the death of her husband Alexander Litvinenko on January 21, 2016 in London, England. Former KGB officer Alexander Litvinenko was poisoned in 2006 with radioactive polonium-210 in the United Kingdom having fled Russia after criticising president Vladimir Putin. (Photo by Ben Pruchnie/Getty Images) (credit:Ben Pruchnie via Getty Images)
Results Of The Inquiry Into The Death Of Alexander Litvinenko Are Published(18 of37)
LONDON, ENGLAND - JANUARY 21: Alexander Litvinenko's widow Marina Litvinenko (centre right) and son Anatoly Litvinenko (right) arrive at The High Court to receive the results of the inquiry into the death of Alexander Litvinenko on January 21, 2016 in London, England. Former KGB officer Alexander Litvinenko was poisoned in 2006 with radioactive polonium-210 in the United Kingdom having fled Russia after criticising president Vladimir Putin. (Photo by Ben Pruchnie/Getty Images) (credit:Ben Pruchnie via Getty Images)
BRITAIN-RUSSIA-POLITICS-SPY-INQUEST-COURT(19 of37)
Marina Litvinenko, widow of Russian former spy Alexander Litvinenko, addresses journalists outside the Royal Courts of Justice in central London on Janurary 21, 2016. Russian President Vladimir Putin 'probably approved' the radiation poisoning of former KGB agent Alexander Litvinenko in London, a British judge said at the conclusion of a public inquiry into his agonising death. Litvinenko was allegedly poisoned at a hotel by a cup of tea laced with polonium-210 -- an extremely expensive radioactive isotope only available in closed nuclear facilities -- in a sequence of events which could have come from a Cold War thriller. AFP PHOTO / NIKLAS HALLE'N / AFP / NIKLAS HALLE'N (Photo credit should read NIKLAS HALLE'N/AFP/Getty Images) (credit:NIKLAS HALLE'N via Getty Images)
Results Of The Inquiry Into The Death Of Alexander Litvinenko Are Published(20 of37)
LONDON, ENGLAND - JANUARY 21: Marina Litvinenko speaks to reporters outside The High Court aftre receiving the results of the inquiry into the death of her husband Alexander Litvinenko, on January 21, 2016 in London, England. Former KGB officer Alexander Litvinenko was poisoned in 2006 with radioactive polonium-210 in the United Kingdom having fled Russia after criticising president Vladimir Putin. (Photo by Dan Kitwood/Getty Images) (credit:Dan Kitwood via Getty Images)
Litvinenko inquiry findings(21 of37)
Marina Litvinenko, the wife of former Russian spy Alexander Litvinenko, speaks to the media outside the Royal Courts of Justice, London, where the findings of the inquiry into his death were revealed. (credit:Jonathan Brady/PA Wire)
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Marina Litvinenko, the wife of former Russian spy Alexander Litvinenko, speaks to the media outside the Royal Courts of Justice, London, where the findings of the inquiry into his death were revealed. (credit:Jonathan Brady/PA Wire)
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Marina Litvinenko, the wife of former Russian spy Alexander Litvinenko, speaks to the media outside the Royal Courts of Justice, London, where the findings of the inquiry into his death were revealed. (credit:Jonathan Brady/PA Wire)
Litvinenko inquiry findings(24 of37)
Marina Litvinenko, the wife of former Russian spy Alexander Litvinenko, speaks to the media outside the Royal Courts of Justice, London, where the findings of the inquiry into his death were revealed. (credit:Philip Toscano/PA Wire)
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Marina Litvinenko, the wife of former Russian spy Alexander Litvinenko, speaks to the media outside the Royal Courts of Justice, London, where the findings of the inquiry into his death were revealed. (credit:Philip Toscano/PA Wire)
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Marina Litvinenko, the wife of former Russian spy Alexander Litvinenko, speaks to the media outside the Royal Courts of Justice, London, where the findings of the inquiry into his death were revealed. (credit:Philip Toscano/PA Wire)
Litvinenko inquiry findings(27 of37)
Marina Litvinenko, the wife of former Russian spy Alexander Litvinenko, speaks to the media outside the Royal Courts of Justice, London, where the findings of the inquiry into his death were revealed. (credit:Jonathan Brady/PA Wire)
Litvinenko inquiry findings(28 of37)
Marina Litvinenko, the wife of former Russian spy Alexander Litvinenko, speaks to the media outside the Royal Courts of Justice, London, where the findings of the inquiry into his death were revealed. (credit:Jonathan Brady/PA Wire)
Britain Poisoned Spy(29 of37)
Marina Litvinenko, widow of former Russian spy Alexander Litvinenko, reads a statement outside the Royal Courts of Justice in London, Thursday, Jan. 21, 2016. British judge Robert Owen is set to release Thursday the findings of a lengthy public inquiry into the 2006 poisoning death of former Russian spy Alexander Litvinenko. One day in 2006, Litvinenko a former KGB agent who claimed to know dark Kremlin secrets had tea with two Russian men at the hotel. Three weeks later, he died of radioactive poisoning after making a deathbed claim that Russian President Vladimir Putin had ordered his killing. (AP Photo/Kirsty Wigglesworth) (credit:Kirsty Wigglesworth/AP)
Britain Poisoned Spy(30 of37)
Marina Litvinenko, widow of former Russian spy Alexander Litvinenko, reads a statement outside the Royal Courts of Justice in London, Thursday, Jan. 21, 2016. British judge Robert Owen is set to release Thursday the findings of a lengthy public inquiry into the 2006 poisoning death of former Russian spy Alexander Litvinenko. One day in 2006, Litvinenko a former KGB agent who claimed to know dark Kremlin secrets had tea with two Russian men at the hotel. Three weeks later, he died of radioactive poisoning after making a deathbed claim that Russian President Vladimir Putin had ordered his killing. (AP Photo/Kirsty Wigglesworth) (credit:Kirsty Wigglesworth/AP)
Britain Poisoned Spy(31 of37)
Marina Litvinenko, widow of former Russian spy Alexander Litvinenko, reads a statement outside the Royal Courts of Justice in London, Thursday, Jan. 21, 2016. British judge Robert Owen is set to release Thursday the findings of a lengthy public inquiry into the 2006 poisoning death of former Russian spy Alexander Litvinenko. One day in 2006, Litvinenko a former KGB agent who claimed to know dark Kremlin secrets had tea with two Russian men at the hotel. Three weeks later, he died of radioactive poisoning after making a deathbed claim that Russian President Vladimir Putin had ordered his killing. (AP Photo/Kirsty Wigglesworth) (credit:Kirsty Wigglesworth/AP)
Litvinenko inquiry findings(32 of37)
Marina Litvinenko, the wife of former Russian spy Alexander Litvinenko, arrives with her son Anatoly at the Royal Courts of Justice, London, where the findings of the inquiry into his death will be revealed. (credit:Philip Toscano/PA Wire)
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Marina Litvinenko, right, widow of former Russian spy Alexander Litvinenko, arrives at the Royal Courts of Justice for the Litvinenko Inquiry statement following publication of the report in London, Thursday, Jan. 21, 2016. A British judge is set to release the findings of a lengthy public inquiry into the 2006 poisoning death of Litvinenko. (AP Photo/Frank Augstein) (credit:Frank Augstein/AP)
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Marina Litvinenko, the wife of former Russian spy Alexander Litvinenko, arrives at the Royal Courts of Justice, London, where the findings of the inquiry into his death will be revealed. (credit:Philip Toscano/PA Wire)
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Marina Litvinenko, the wife of former Russian spy Alexander Litvinenko, arrives at the Royal Courts of Justice, London, where the findings of the inquiry into his death will be revealed. (credit:Philip Toscano/PA Wire)
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Marina Litvinenko, the wife of former Russian spy Alexander Litvinenko, arrives at the Royal Courts of Justice, London, where the findings of the inquiry into his death will be revealed. (credit:Philip Toscano/PA Wire)
Results Of The Inquiry Into The Death Of Alexander Litvinenko Are Published(37 of37)
LONDON, ENGLAND - JANUARY 21: Marina Litvinenko speaks to members of the press outside The High Court after receiving the results of the inquiry into the death of her husband Alexander Litvinenko on January 21, 2016 in London, England. Former KGB officer Alexander Litvinenko was poisoned in 2006 with radioactive polonium-210 in the United Kingdom having fled Russia after criticising president Vladimir Putin. (Photo by Ben Pruchnie/Getty Images) (credit:Ben Pruchnie via Getty Images)