Diego Garcia Military Base and British Indian Ocean Territory Bill: Reasoned Amendment
116
Ayes
—
333
Noes
Defeated · Government won
198 did not vote
Analysis
Commons
Commons
**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.
Voting Aye meant
Oppose the Chagos treaty and its implementing Bill, arguing the deal is not in the UK's national or security interest and should not proceed
Voting No meant
Support proceeding with the Bill to implement the Chagos treaty, arguing the 99-year guarantee of Diego Garcia's operational control secures UK and allied defence interests
449 voting MPs. Each dot is one vote; left-to-right by party. Grey dots in the centre are the 198 who did not vote.
Aye
No
Absent
Labour PartyWhipped No
0
285
77
Conservative and Unionist PartyWhipped Aye
100
0
16
Liberal Democrats
0
0
72
Labour and Co-operative PartyWhipped No
0
35
7
Independent
3
7
3
Scottish National Party
0
0
9
Reform UKWhipped Aye
8
0
—
Sinn Féin
0
0
7
Democratic Unionist PartyWhipped Aye
5
0
—
Green Party of England and WalesWhipped No
0
3
1
Plaid Cymru
0
0
4
Social Democratic and Labour Party
0
2
—
Alliance Party of Northern Ireland
0
0
1
Speaker
0
0
1
Traditional Unionist Voice
1
0
—
Ulster Unionist Party
1
0
—
Your Party
0
1
—
Defends the treaty as securing critical defence interests against legal threats; claims the previous Conservative government started negotiations for the same reason; attacks Opposition for not publishing their own negotiating position.Labour · Voted no · Read full speech (6,936 words) →
Opposes the bill as an unjustified surrender of sovereignty, arguing the UK paid for freehold ownership in the 1960s and is now renting back at £35 billion cost; rejects legal threat narrative and argues previous Foreign Secretary Cameron ended negotiations, not left a deal.Conservative · Voted aye · Read full speech (5,932 words) →
Questions whether the deal retains rolling sovereignty after 99 years and challenges the government's claimed compensation to Mauritius, asserting Labour has capitulated compared to Conservative negotiating position.Conservative · Voted aye · Read full speech (208 words) →
Argues the ICJ judgment was not legally binding on the UK and criticises use of Net Present Value methodology to justify the cost, which conflates commercial accounting with sovereign treaty obligations.Conservative · Voted aye · Read full speech (2,780 words) →
Demands a full apology (not just regret) for Chagossian treatment; notes legal judgment supports return to Mauritius; seeks clarity on resettlement rights and Diego Garcia access for displaced islanders.Independent · Voted no · Read full speech (1,877 words) →
Questions whether the 99-year lease with only first refusal truly secures the base long-term; warns Britain becomes hostage to future Mauritian decisions and risks losing the base in four generations.Conservative · Voted aye · Read full speech (3,644 words) →
Challenges the government's costings and accounting methodology, citing disagreement with the Government Actuary's Department and Office for Budget Responsibility; questions why NPV has not been used in comparable government decisions.Conservative · Voted aye · Read full speech (406 words) →
Supports the deal; notes US Defence Secretary and President Trump endorsement; questions why Conservatives who negotiated 85% of the treaty now oppose it from opposition benches.Labour · Voted no · Read full speech (2,131 words) →
Sources
Division dataUK Parliament Votes API
DebateHansard · Commons
Stance analysisAI analysis · Claude 4.x
LicenceOpen Parliament Licence v3.0