Diego Garcia Military Base and British Indian Ocean Territory Bill: Reasoned Amendment
116Ayes
333Noes
Defeated · majority 217 · Government won198 did not vote
647 Members · Aye 116 · No 333 · DNV 198 · grey dots in centre are abstentions
Analysis
Commons
Commons
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. 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 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
Each row is one party. The stacked bar gives the within-party split of Aye / No / Absent; the columns on the right give the raw counts. The whip column shows the published party position — “Free vote” means the whip was formally removed for this division.
Party
Whip
Aye / No / Abs
Aye
No
Abs
Labour Party
Whipped No
0
284
77
Conservative and Unionist Party
Whipped Aye
100
0
16
Liberal Democrats
—
0
0
72
Labour and Co-operative Party
Whipped No
0
35
7
Independent
—
2
8
3
Scottish National Party
—
0
0
9
Reform UK
Whipped Aye
8
0
0
Sinn Féin
—
0
0
7
Democratic Unionist Party
Whipped Aye
5
0
0
Green Party of England and Wales
Whipped No
0
3
1
Plaid Cymru
—
0
0
4
Social Democratic and Labour Party
—
0
2
0
Alliance Party of Northern Ireland
—
0
0
1
Restore Britain
—
1
0
0
Speaker
—
0
0
1
Traditional Unionist Voice
—
1
0
0
Ulster Unionist Party
—
1
0
0
Your Party
—
0
1
0
Source · Hansard · UK Parliament Votes API · whip status from announced positions; “free vote” indicates the whip was formally removed
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