Argentina's president Cristina Fernandez de Kirchner challenged the British sovereignty of the Falkland Islands on Thursday evening calling it an "affront to the world."
Her demand for negotiation over the islands sovereignty came as the two countries marked 30 years since the end of the Falklands war.
Addressing the UN Committee on Decolonisation in New York on Thursday night, President Kirchner said distance undermined the UK's argument.
"How can it be claimed that, 14,000 kilometres away, that it can be part of the British territory?" she said.
"The UK is benefiting from its privileged position as a permanent member of the security council of the United Nations."
The head of state said the dispute was a challenge to the international community to overcome outdated "prejudice and cliches".
She insisted Argentina just wanted to "talk" about the islands' sovereignty.
"Can someone in the modern world deny that possibility?" she added.
However the Prime Minister told a reception in London that there would be "no negotiation" - and warned that Britain would defend the territory by force again if necessary.
In a speech at the annual Falkland Islands government reception last night, David Cameron said the Falklands was enjoying economic growth and industries such as tourism and fishing were "thriving".
"There is only one shadow on the horizon. And that is the aggression from over the water," Cameron said.
"With Argentina in particular there are so many things we should be working together on - managing fish stocks, increasing trade, environmental issues. This is the kind of co-operation we need - and that's why we want to have a reasonable, sensible relationship with Argentina.
"But let me be equally clear on this - when it comes to the sovereignty of the Falkland Islands, there will be absolutely no negotiation.
"This is not some game of global Monopoly, with nations passing a territory between them. It's about the islanders determining their own future.
"This has been their home for almost 180 years. There are children whose ancestors have lived there for generations. The roots go deep, and they will not be ripped out."
But Kirchner has said the government should feel "shame" for flying the Falklands flag, telling the UN: “When I looked today at 10 Downing Street and saw them and what they were doing with the flag which they call the Falkland Islands flag, I felt shame from afar for them because wars are not to be celebrated nor are they to be commemorated. Do you know why? Because many people lost their lives.”
The comments came after war heroes and those they freed paid a series of moving tributes to the fallen.
Around 400 islanders gathered next to Liberation Memorial in Stanley yesterday to thank those who ended the 74-day occupation of the remote British Overseas Territory.
A thick snow storm began as Falklanders, veterans and VIPs left a service of thanksgiving held at Stanley's Christ Church Cathedral.
Young and old packed into the church with standing room only at the back to take part in the commemoration to those who died in 1982.
The brief but bitter war ended on June 14 1982 as Argentinian commander General Mario Menendez surrendered to the British at Stanley.
The fighting cost the lives of 255 British servicemen, three Falkland Islanders and 655 Argentinian soldiers.
About 30 veterans braved the cold to proudly lead a parade of servicemen from the Royal Navy, the Parachute Regiment, the Royal Air Force and the Falkland Islands Defence Force.
The service was attended by Foreign Office minister Jeremy Browne, who said: "I think it is hard to convey to anybody who isn't here, who is back home in Britain, just how much this means to the Falkland Islanders."
Cameron later highlighted a planned referendum of Islanders on whether they wish to remain linked to the UK. He told the reception: "My message to the government of Argentina is this: the UK has no aggressive intentions towards you. Accusations of militarisation and nuclear threats are hyperbole and propaganda.
"But do not under-estimate our resolve. Threats will not work, attempts to intimidate the islanders will not succeed, because Britain stands ready and willing to stand up for the Falkland Islanders at any time.
"As long as they wish to remain a British territory, that is the way it will stay."
Argentina's President Cristina Fernandez
Argentina's President Cristina Fernandez de Kirchner listens during a meeting at the United Nations headquarters in New York on the disputed Falkland Islands on the 30th anniversary of the end of war between the Britain and Argentina, on June 14, 2012. Argentina has said Britain has 'a duty' to negotiate the future of the Falkland Islands. Kirchner leads delegation of more than 90 Argentine diplomats and officials at the UN decolonization committee's annual meeting on the Falklands and 15 other territories around the world. Two Falkland Islands assembly members will put the case that the 3,000 Falklanders want to remain under the British flag. AFP PHOTO/Mehdi Taamallah (Photo credit should read MEHDI TAAMALLAH/AFP/GettyImages)
Picture of Port Stanley, in the Falkland
Picture of Port Stanley, in the Falkland Islands, taken on March 29, 2012. Next April 2 marks the 30th anniversary of the war between Britain and Argentina for the possession of the islands. AFP PHOTO/MARTIN BERNETTI (Photo credit should read MARTIN BERNETTI/AFP/GettyImages)
Argentinian Marcelo Wytrykusz, veteran o
Argentinian Marcelo Wytrykusz, veteran of the 1982 South Atlantic war between Argentina and Britain over the Falkland Islands (Malvinas), remains chained to the fence of the building of Argentine oil company YPF, in Buenos Aires, on June 5, 2012. Wytrykusz, member of the National Resistance movement, is protesting against the contracting -by recently nationalized YPF- of the 'Stena Polaris', a ship of British, flag for the transportation of oil from Tierra del Fuego to Buenos Aires. AFP PHOTO/ALEJANDRO PAGNI (Photo credit should read ALEJANDRO PAGNI/AFP/GettyImages)
A map of the Falkland Islands is inscri
A map of the Falkland Islands is inscribed in stone during the dedication ceremony of the Falklands Memorial at the National Memorial Arboretum in Alrewas, central England on May 20, 2012. More than 600 veterans and family members gathered to commemorate the 30th Anniversary of the Task Force Landings on the Falkland Islands. Initiated by The South Atlantic Medal Association 1982, the Falklands Memorial has been built to honour the Task Force and to remember the 255 UK servicemen and merchant seamen who gave their lives in the Falklands Conflict. AFP PHOTO/PAUL ELLIS (Photo credit should read PAUL ELLIS/AFP/GettyImages)
Tour guide Derek Pettersson shows the wr
Tour guide Derek Pettersson shows the wreckage of an Argentine trench, used during the 1982 conflict, near Port Stanley, in the Falkland Islands, on March 29, 2012. Next April 2 marks the 30th anniversary of the war between Britain and Argentina for the possession of the islands. AFP PHOTO / MARTIN BERNETTI (Photo credit should read MARTIN BERNETTI/AFP/GettyImages)
View of the St Mary's Church in Port Sta
View of the St Mary's Church in Port Stanley, in the Falkland Islands, on March 28, 2012. April 2, 2012 commemorates the 30th anniversary of the war between Britain and Argentina for the possession of the islands. AFP PHOTO / MARTIN BERNETTI (Photo credit should read MARTIN BERNETTI/AFP/GettyImages)
The flag of the Falkland Islands flies o
The flag of the Falkland Islands flies over number 10 Downing Street in central London on June 14, 2012. Britain's premier vowed on June 14 to defend the Falklands from Argentinian 'aggressive threats' as the 30th anniversary of the end of the war over the islands was marked in London and Port Stanley. AFP PHOTO / LEON NEAL (Photo credit should read LEON NEAL/AFP/GettyImages)
Argentinian Marcelo Wytrykusz, veteran o
Argentinian Marcelo Wytrykusz, veteran of the 1982 South Atlantic war between Argentina and Britain over the Falkland Islands (Malvinas), remains chained to the fence of the building of Argentine oil company YPF, as a British flag is burnt in Buenos Aires, on June 5, 2012. Wytrykusz, member of the National Resistance movement, is protesting against the contracting -by recently nationalized YPF- of the 'Stena Polaris', a ship of British, flag for the transportation of oil from Tierra del Fuego to Buenos Aires. AFP PHOTO/ALEJANDRO PAGNI (Photo credit should read ALEJANDRO PAGNI/AFP/GettyImages)
Argentine President Cristina Fernandez d
Argentine President Cristina Fernandez de Kirchner delivers a speech during a ceremony to mark the 30th Anniversary of the 1982 South Atlantic war between Argentina and the Britain over the Falkland Islands (Malvinas), in Ushuaia, Tierra del Fuego, some 3100 km south of Buenos Aires, Argentina on April 2, 2012. Britain and Argentina on Monday marked 30 years since an Argentine invasion of the Falklands Islands triggered a bloody 74-day war, amid renewed tensions between the two countries. AFP PHOTO/JUAN MABROMATA (Photo credit should read JUAN MABROMATA/AFP/Getty Images)