President Fernández uses letter to David Cameron in British press to say Britain should open sovereignty talks over islands

Thirty years after Britain and Argentina went to war over the Falklands, Argentina's populist president, Cristina Fernández de Kirchner, has returned to the fray with a blistering attack on British "colonialism" and a demand to hand back "Las Malvinas".

In a stinging letter to David Cameron, Fernández urges the UK to abide by a 1960 United Nations resolution urging member states to "end colonialism in all its forms and manifestations".

Britain should begin negotiations over the sovereignty of the islands, which were "forcibly stripped" from Argentina exactly 180 years ago, on 3 January 1833, she tells the prime minister.

Her letter is published as an advert (pdf) inThursday's Guardian and other newspapers. Fernández acidly notes that the "Malvinas" are 8,700 miles away from London and claims, controversially, that the Royal Navy expelled the Argentinians who originally lived on the remote South Atlantic territory. Replacing them with British settlers was, she says, a "blatant exercise in nineteenth-century colonialism".

Fernández's diplomatic broadside follows the British government's decision last month to name a large frozen chunk of Antarctica after the Queen – a gesture viewed in Buenos Aires as provocative. Argentina also lays claim to what is now Queen Elizabeth Land, as well as to other South Atlantic dependencies including South Georgia and the uninhabited South Sandwich Islands.

The president and her advisers seem convinced that by keeping the issue of the Falklands in the public eye she can embarrass London into eventual negotiations. In her letter, Fernández claims not only Latin America but also the "vast majority of peoples and governments around the world" embrace Argentina's claim and "reject colonialism".

Critics suggest that Fernández, an unashamed populist and nationalist, is seeking to deflect attention from social disharmony at home. The president's approval rating is sagging ahead of mid-term legislative elections in October. Argentinians support the "Malvinas" cause, which is written into the constitution. But they are also worried about pressing economic problems such as inflation, rising crime and corruption.

The Foreign and Commonwealth Office (FCO) has categorically ruled out any new negotiations saying the future of the Falklands can only be decided by the islanders themselves in accordance with the UN principle of self-determination. The islanders are due to vote in a referendum later this year, which is expected to give overwhelming backing for the territory to remain British.

The FCO also disputes Fernández's claim that Britain kicked out the island's original Argentinian inhabitants. It says there was no civilian population on the island in 1833, with the Royal Navy expelling an Argentine military garrison that had arrived three months earlier. "We can't talk about sovereignty unless and until the Falkland islanders agree to it," the FCO said.

Robert Munks, deputy editor at Jane's Intelligence Review, said Fernández's latest PR offensive over the Falklands, which follows adverts last year on the anniversary of the war, was "not entirely surprising".

He said there had been a "significant slump" in UK-Argentinian relations since 2003, when Fernández's late husband, Néstor Kirchner, came to power.

"Relations are probably at their worst now than at any time since 1982 and the Falklands war. That's not to say there is any possibility of an armed conflict. There will not be another war. What the Argentinians have done is pull out of a number of bilateral agreements from the 1990s," Munks said.

Indeed, Buenos Aires has terminated practical co-operation with the UK over South Atlantic issues such as fishing and oil. Both sides had agreed to discuss the lucrative hydrocarbons discovered off the Falklands islands in 1998 separately from any territorial claims. The Fernández government has broken off talks and insists the sovereignty dispute must be resolved first.

The advert in Thursday's Guardian seems to have been prepared in absolute secrecy to ensure maximum impact. A source at Fernández's press office said that even they had been kept in the dark about it. "These kind of decisions are handled in strict secrecy at the highest level to maximise the surprise effect," said the source.

According to Munks, this latest row is replete with historical ironies. At one point, Spain, France, Britain and Argentina have all laid claim to the Falklands. "The colonial history of possession and dispossession is complex and disputed," he said.

He added: "The FCO in the 60s and 70s was looking for ways to divest itself of these islands.

"Were it not for the invasion, the likelihood is that Argentina by now would have some form of sovereignty over the Falklands."