The Foreign Office does not recognise Mauritius’ claim to sovereignty over the islands, one of which is home to a US airbase.
Britain has been accused of acting like an illegal colonial occupier for refusing to hand back control of a remote set of islands in the Indian Ocean.
The Chagos Islands were due to be given back to Mauritius by Friday following an overwhelming vote at the UN General Assembly in May.
The Foreign Office says it does not recognise Mauritius’ claim to sovereignty over the archipelago, located 310 miles (500km) from the Maldives, which used to be a British colony.
It insists it has every right to hold onto the islands – one of which, Diego Garcia, is home to a US military airbase.
In order to build the base, Britain expelled thousands of Chagossians from their homelands between 1968 and 1974.
They were sent more than 1,000 miles away to Mauritius and the Seychelles, where they faced extreme poverty and discrimination.
Labour leader Jeremy Corbyn, who has campaigned for Britain to hand them back, said the news shows the government “shamefully considers itself to be above international law”.Donald Trump impeachment inquiry: President’s ex-adviser says Russia ‘gearing up’ to interfere in 2020 US election
He promised to “end colonial rule” if his party won power at the election.
The Chagos Archipelago was separated from Mauritius in 1965, when Mauritius was still a British colony. Britain purchased it for £3m – creating the British Indian Ocean Territory.
Mauritius claims it was forced to give it up in exchange for independence, which it gained in 1968.
In May, the UN General Assembly voted to return the islands to Mauritius within six months, with 116 states backing the move and only six against.
Three months earlier, the UN’s high court urged Britain to leave the islands “as rapidly as possible”.
The UN said that the decolonisation of Mauritius “was not conducted in a manner consistent with the right to self-determination” and that therefore the “continued administration… constitutes a wrongful act”.
As the six-month period came to a close, Mauritian Prime Minister Pravind Jugnauth said the UK was now an illegal colonial occupier, the BBC said…