Britain accused Argentina of colonialism in its claim to the Falkland Islands on Wednesday, as the 30th anniversary of their conflict over the British-ruled territory approaches.

A day after Britain's National Security Council discussed the Falklands' defences, Prime Minister David Cameron told parliament Britain was committed to protecting the South Atlantic islands and added that people there should be allowed to decide their own nationality.

Cameron said he was determined that the islands' defences were in order and that islanders' wishes were paramount. We support the Falkland islanders' right to self-determination, he said.

What the Argentinians have been saying recently I would argue is actually far more like colonialism because these people want to remain British and the Argentinians want them to do something else.

Argentine President Cristina Fernandez described Britain last June as a crass colonial power in decline for refusing to hold talks over the islands, known as Las Malvinas in Spanish, and Argentine officials were quick to hit back over Cameron's remarks on Wednesday.

It's totally offensive, said Interior Minister Florencio Randazzo, while Foreign Minister Hector Timerman described Britain as a synonym for colonialism.

Evidently at a time when only scraps of colonialism linger, Great Britain ... has decided to rewrite history, Timerman told the state news agency.

London has controlled the islands, about 300 miles (480 km) off the Argentine coast, since 1833. Its two-month war with Argentina in 1982 resulted in the deaths of 255 British and about 650 Argentine soldiers.

The British government says it will only agree to sovereignty talks if the territory's 3,000 residents ask it to, and that the islanders want to remain British.

Tensions have risen in recent years over offshore oil exploration, and have gained steam before the April anniversary of the conflict as well as the planned tour of duty on the islands by Prince William, an RAF helicopter pilot, later this year.

In December, the South American trading bloc Mercosur - including associate member Chile - agreed that vessels sailing under a Falklands Islands flag would be banned from docking at any of its ports as an act of solidarity with Argentina.

Foreign Secretary William Hague, visiting Mercosur's economic powerhouse Brazil, discussed the Falklands in Brasilia on Wednesday, but the Brazilian government said it backed Argentina in the dispute and would apply the shipping ban.

Hague said differences over the Falklands did not prevent a vastly productive relationship and growing friendship with Brazil, whose economy is now the size of Britain's.

He knows that Brazil, and all Latin American and Caribbean countries, support Argentine sovereignty over the Falklands, Brazilian Foreign Minister Antonio Patriota told reporters.

We have to abide by Mercosur's resolutions, Defense Minister Celso Amorim told Reuters after meeting with Hague. Besides, he added, Argentina is our number one strategic ally.

(Additional reporting by Adrian Croft in London, Helen Popper in Buenos Aires and Anthony Boadle in Brasilia; Editing by Paul Simao)