David Cameron insisted Britain was "toughening" up its response to Russia after a public inquiry implicated Vladimir Putin in the assassination of Alexander Litvinenko but conceded the UK must continue to have "some sort" of relationship with Moscow.
The Prime Minister said the UK would deal with Russia with "clear eyes and a very cold heart" following publication of Sir Robert Owen's report, which found the president "probably" signed off the poisoning of the dissident with radioactive polonium in London in 2006.
Speaking in Davos, Mr Cameron described the state-sponsored murder as "absolutely appalling" but said the inquiry report confirms what "we have always believed" had happened.