Argentina's President Cristina Kirchner and Prime Minister David Cameron clashed publicly at the G20 summit over the future of the disputed Falkland Islands.
Argentinian officials branded the British leader a "colonialist" in dismissing Kirchner's call for talks on the sovereignty of the islands, while Cameron said he had been attempting to counter Argentina's "propaganda".
The pair came face-to-face at the meeting of the world's major economies in Mexico, at a time when tensions between their countries were already running high just days after the 30th anniversary of the Falklands War.
Cameron urged Kirchner to respect the will of the 3,000 residents on the South Atlantic islands, who want to remain British. Kirchner countered him by citing UN resolutions calling for sovereignty negotiations.
"The president had the UN resolutions and she said to Cameron: 'Let's respect the United Nations'," Argentina's Foreign Minister Hector Timmerman said.
"The prime minister refused to accept the documents, turned his back and walked away without a farewell," he added, accusing Britain of disrespecting UN resolutions and of retaining an imperialist mindset.
"After years of acting as a colonial power they have forgotten that they are responsible for the existence of colonialism, and that it is countries like Argentina that defeated most of the colonial projects in the world," he said.
Cameron confirmed he approached Kirchner in order to urge her to respect the right of Falkland Islanders to choose their own future in an upcoming referendum that is expected to show overwhelming opposition to Argentinian rule.
"We should be clear that because there's a referendum there's an opportunity for those countries in the world who have not looked at this issue for a while and have perhaps accepted some of the propaganda put around by Argentina or its supporters to look again at this issue and recognize that the people of these islands should be able to determine their own future," he said.
"It's an important point to make to the Argentine president and an important point to make more widely and that's exactly why I did what I did."
A Downing Street source, speaking on condition of anonymity, confirmed that there had been a tense exchange, but downplayed the allegation that Cameron had refused to accept a packet of documents from Kirchner.
"He took it up to her to make those points. She took that badly and that was basically it," she said.
"I don't think it was actually totally clear that she was trying to give him documents.... We're following up with Argentinian officials here to see if there are any documents they want to give us."
In 1982 Argentina's former military regime invaded and occupied the Falkland Islands, which are known as the Malvinas in Spanish.
Britain promptly dispatched a naval task force to the South Atlantic and recaptured the territory after a brief but fierce war which left 255 British soldiers and 650 Argentines dead.
Argentina now has an elected civilian government and Kirchner has called for negotiations with Britain on the islands' future.
British officials accuse her of stirring nationalist passions for domestic political gain, and Cameron has refused to discuss the issue of sovereignty.