The UK has been called an illegal colonial occupier by Mauritius after it ignored a deadline to return control of an overseas territory to the island nation.
The UN had given the UK six months to give up control of the Chagos Islands – but that period has now passed.
Mauritius says it was forced to trade the small archipelago in the Indian Ocean in 1965 for independence.
The UK says it does not recognise Mauritius’ claim to sovereignty.
Britain’s Foreign and Commonwealth Office (FCO) insists it has every right to hold onto the islands – one of which, Diego Garcia, is home to a US military airbase.
“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.”