The deal to transfer the Indian Ocean archipelago to Mauritius includes the tropical atoll of Diego Garcia, home to a military base used by the UK and the US that plays a crucial role in the region’s stability and international security.

Under the agreement, the base will remain under UK and US jurisdiction for at least the next 99 years.

The UK government said that the treaty would “address wrongs of the past and demonstrate the commitment of both parties to support the welfare” of Chagossians - the native people of the islands.

Several leading Conservatives have called the decision “weak”, with former securities minister Tom Tugendhat saying it is a “shameful retreat undermining our security and leaving our allies exposed”.

Since 1971, only Diego Garcia has been inhabited - by US military employees - after the UK expelled the Chagossians at the request of the US. Some moved to Mauritius and some have lived in the UK, in Crawley, West Sussex, since 2002.

The islands had been a dependency of Mauritius when it was a French colony, but both were handed to the UK in 1845. Mauritius gained independence from the UK in 1968 and has since claimed the Chagos archipelago as Mauritian.