Diego Garcia Military Base and British Indian Ocean Territory Bill Committee: Amendment 7

Parliament voted on 20 October 2025 on Amendment 7 to the Diego Garcia Military Base and British Indian Ocean Territory Bill, during the bill's committee stage. The amendment, tabled by Conservative MPs, would have required the Secretary of State to lay before Parliament a memorandum explaining the legal basis under international law for transferring sovereignty of the British Indian Ocean Territory to Mauritius before the treaty and the bill's key provisions could come into force. That memorandum would have had to include a summary of legal advice received, an analysis of the UK's sovereignty status under international law, the legal argument for ceding sovereignty, and an assessment of the risks had no deal been struck. The amendment was defeated by 321 votes to 174. The bill implements a treaty signed on 22 May 2025 under which Mauritius becomes sovereign over the Chagos Archipelago, including Diego Garcia. It dissolves the British Indian Ocean Territory in domestic law and removes it from the list of British overseas territories in the British Nationality Act 1981. The UK retains rights to administer and operate the Diego Garcia military base under terms granted by Mauritius. Amendment 7 would have inserted a delay mechanism: neither the treaty nor the operative clauses of the bill could take effect until the legal memorandum had been laid before Parliament, with a two-month deadline from Royal Assent. Its defeat means the bill can proceed without that condition being met. All 272 Labour and 33 Labour and Co-operative Party members who voted opposed the amendment. The Conservatives were unanimously in favour, joined by all 64 Liberal Democrats who voted, all 7 Reform UK members, all 4 Democratic Unionist Party members, and 3 independents. Plaid Cymru, the Green Party, and the Your Party grouping all voted against. The vote was one of several on the same day: a related division on New Clause 1 fell 322 to 172, and the bill passed its Third Reading 320 to 171, confirming that the government's majority held consistently throughout.