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

What happened: The House of Commons voted on 9 September 2025 on a reasoned amendment to the Diego Garcia Military Base and British Indian Ocean Territory Bill. A reasoned amendment is a procedural motion that, if passed, would have blocked the Bill from progressing by stating the House's reasons for declining to give it a second reading. The amendment was defeated by 333 votes to 116, allowing the Bill to continue its parliamentary passage.

Why it matters: The Bill concerns the legal and treaty framework governing the Diego Garcia military base in the British Indian Ocean Territory, one of the most strategically significant military installations in the world, used jointly by the United Kingdom and the United States. By defeating the blocking amendment, the Commons permitted the legislation to advance, which relates to the government's broader approach to the territory, including arrangements with Mauritius over sovereignty and continued military access. The outcome has implications for UK-US defence cooperation, the future of the base, and the rights of the Chagossian people displaced from the territory.

The politics: The vote divided largely along government-versus-opposition lines. All 285 Labour MPs and all 35 Labour and Co-operative MPs voted against the amendment, supporting the Bill's progress. The Conservatives provided the bulk of the 116 ayes, with all 100 voting Conservative MPs backing the amendment to block the Bill, joined by all 8 Reform UK MPs, all 5 Democratic Unionist Party MPs, and 1 Ulster Unionist MP. Three independents voted to block while seven voted with the government. The Greens, SDLP, and Your Party voted with the government against the amendment. This vote sits within a cluster of related divisions, with Commons committee stage votes on amendments to the same Bill following in October 2025.