The Foreign Office has moved to allay concerns raised by former prime minister Boris Johnson that handing over the Chagos Islands to Mauritius could play into China's hands.
He described the move as “utterly spineless” and said the UK appeared “on the verge of a colossal mistake”, calling Mauritius' claim to the islands “absurd”.
The UK has opened negotiations with Port Louis over the future of the Chagos Islands following international pressure.
The United Nations' top court, the International Court of Justice, has ruled that the UK's administration of the territory is “illegal” and must end after two centuries of British control.
But the Conservative Government said that regardless of the outcome of talks between the two countries, a joint UK-US military base in Diego Garcia, one of the Indian Ocean island group that makes up the Chagos Islands, would continue to operate . from the allies.
It comes after Mr Johnson said in his weekly column for the Daily Mail that he had been told by an “informant” that it was a “done deal” that the UK would hand over the Chagos Islands to the Commonwealth nation's control.
Mr Johnson pointed to the importance of one of the volcanic islands, Diego Garcia, to the relationship between Britain and the US, as it was used as a base during the first and second Gulf wars, as well as the Allied invasion of Afghanistan.
The former Tory leader said: “The Americans are not giving us critical nuclear secrets just because they love little old England.
“They don't share intelligence because they love our quaint accents. We have a great and necessary relationship because we have important things to offer – including Diego Garcia.
“Who knows what will happen if we give up sovereignty. The Mauritians might cut out the middleman and do a deal with the US (and they don't mind the Chagossians).
“But then a future Mauritian government may also close the base or allow the Chinese, for the right price, to build their own runways in the same archipelago.”
Foreign Office officials said the UK government was working “in lockstep” with the US during talks on the future of the Chagos Islands and said it had Washington's “full support” on all elements of the negotiation.
The ministry said it would not be appropriate to speculate on the outcome of the talks while they were ongoing.
A spokesman for the Foreign, Commonwealth and Development Office said: “The UK and Mauritius have held five rounds of constructive negotiations on the exercise of sovereignty over the British Indian Ocean Territory/Chagos Archipelago and officials will meet again shortly to continue negotiations.
“The UK and Mauritius have reiterated that any agreement between our two countries will ensure the continued effective operation of the UK joint military base at Diego Garcia, which plays a vital role in regional and global security.”
Chagossians have spent decades fighting to return to the islands after more than 1,000 people were forced to leave in the 1960s and 1970s to make way for the military base.
Thousands of Chagossians now live around the world, mainly in Mauritius, the United Kingdom and the Seychelles.
In a written ministerial statement released earlier this month, junior foreign minister David Rutley said Prime Minister Rishi Sunak had met his Mauritian counterpart on the sidelines of the G20 summit in New Delhi, India, to assess the progress of negotiations. .
Further negotiations are expected this month, he said.