Diego Garcia Military Base and British Indian Ocean Territory Bill: Third Reading

Parliament voted on 20 October 2025 to pass the Diego Garcia Military Base and British Indian Ocean Territory Bill at Third Reading (the final Commons stage before the bill moves to the Lords), by 320 votes to 171. The bill transfers sovereignty over the Chagos Archipelago, including Diego Garcia, from the United Kingdom to Mauritius, while allowing the UK to continue operating its military base on Diego Garcia under a lease arrangement agreed in a treaty signed on 22 May 2025. The bill ends the British Indian Ocean Territory as a British overseas territory in domestic law, removes it from the list of such territories in the British Nationality Act 1981, and preserves existing laws of the territory to ensure continuity. In practical terms, the UK gives up sovereign control over the archipelago in exchange for continued operational rights over the Diego Garcia base, which hosts significant US and UK military assets. The bill also closes future entitlement to British Overseas Territories citizenship based on Chagos connections, while preserving existing transitional routes to British citizenship for eligible Chagossians until current statutory deadlines. The vote divided almost entirely along party lines. All 303 Labour and Labour and Co-operative MPs who voted backed the bill; Conservatives, Liberal Democrats, Reform UK, and the Democratic Unionist Party all voted against. Four independents and all four Plaid Cymru MPs voted with the government, as did all three Green MPs who voted. There were no Conservative or Liberal Democrat votes in favour. The Conservatives framed the bill throughout proceedings as a "surrender" of British territory for a cost to the taxpayer of £35 billion, and raised concerns about Mauritius's relationships with China and Russia.