Argentina and Britain went to war over the Falklands in 1982
The government has firmly rejected the latest claim by Argentina to sovereignty over the Falkland Islands, MPs have been told.
In a written statement, junior Foreign Office minister Chris Bryant said the UK had "no doubt" that the Falklands belonged to the UK.
Argentina passed a law in December claiming to own the islands and several other British overseas territories.
The Conservatives gave their "full support" to the government's response.
Argentina and Britain went to war over the Falklands in 1982, and despite the former's surrender, the South American state has maintained claims to the islands ever since.
Mr Bryant said the Foreign Office had delivered a "note verbale" to the Argentine charge d'affaires in London to outline UK rejection of the claim.
It insisted that the Falklands, along with South Georgia, the South Sandwich Islands and the British Antarctic Territory, all remained firmly under UK sovereignty.
Shadow foreign minister David Lidington added that the Conservatives would "condemn attempts by any foreign governments to assert otherwise".
In March 2009, Gordon Brown rejected calls from Argentina for talks over the future sovereignty of the Falklands.
He turned down the request for discussions at a meeting with the country's president, Cristina Fernandez.