The UK has defied a United Nationals deadline to return control of an overseas territory to Mauritius.
The UN gave the UK six months to give up control of the Chagos Islands, but the deadline passed on Friday.
The UK’s refusal to end its occupation of the Indian Ocean archipelago is expected to be marked by protests outside the UK high commission in the Mauritian capital, Port Louis, by those who were forcibly deported more than 40 years ago and their descendants.
Britain purchased the Chagos Archipelago for £3 million after it was separated from Mauritius in 1965, when the island nation was still a British colony.
Mauritius claims it was forced to give it up in exchange for independence, which it gained in 1968.
Mauritian Prime Minister Pravind Jugnauth said the UK was now an illegal colonial occupier, according to the BBC.
In May, the UN General Assembly voted by an overwhelming majority of 116 to six countries in favour of a motion condemning Britain's occupation and demanding, what is known as the British Indian Ocean Territory, be reunified with Mauritius.
The UN resolution came only three months after the UN's high court advised the UK should leave the islands "as rapidly as possible".
The UK regards neither the ICJ judgment nor the UN motion as binding.
Britain's Foreign and Commonwealth Office (FCO) said in a statement: "The UK has no doubt as to our sovereignty over the British Indian Ocean Territory (BIOT), which has been under continuous British sovereignty since 1814," it said in a statement.
"Mauritius has never held sovereignty over the BIOT and the UK does not recognise its claim."
The Labour party’s election manifesto, published on Thursday, pledges to allow Chagossians to resettle in their homeland.
At the time of the UN resolution, the FCO said the UK would stand by an earlier commitment to hand over control of the islands when they were no longer needed for defence purposes.
Between 1968 and 1974, Britain forcibly removed thousands of Chagossians from their homelands and sent them to Mauritius and the Seychelles, where they faced extreme poverty and discrimination.
Many moved to the UK in the hope of a better life.
Britain then invited the US to build a military base on Diego Garcia, one of the islands in the archipelago.
