Diego Garcia Military Base and British Indian Ocean Territory Bill: Second Reading
330Ayes
179Noes
Carried · majority 151 · Government won140 did not vote
649 Members · Aye 330 · No 179 · DNV 140 · grey dots in centre are abstentions
Analysis
Commons
Commons
MPs voted 330 to 179 on 9 September 2025 to give the Diego Garcia Military Base and British Indian Ocean Territory Bill its Second Reading, allowing it to proceed through Parliament. The Bill implements the treaty signed on 22 May 2025 between the UK and Mauritius, under which Mauritius becomes sovereign over the Chagos Archipelago while the UK retains the right to operate the Diego Garcia military base for 99 years. The Bill, if it becomes law, will dissolve the British Indian Ocean Territory as a British overseas territory in domestic law, remove it from the list of British overseas territories in the British Nationality Act 1981, and preserve existing BIOT laws as laws of Diego Garcia to ensure continuity. It also amends British nationality law, removing the future right to acquire British Overseas Territories citizenship through Chagos connections while preserving existing transitional routes to British citizenship for eligible Chagossians. The practical stakes are significant: the Diego Garcia base supports UK and US military operations across the Middle East, east Africa and south Asia, and hosts deepwater port, airfield, and surveillance capabilities used in counter-terrorism operations. Labour MPs voted almost unanimously in favour, while Conservatives, Liberal Democrats, and Reform UK voted against as a bloc. No Conservative or Liberal Democrat MP voted for the Bill. Seven independents voted aye and two voted no, while the Greens and the Social Democratic and Labour Party also voted with the government. The vote reflects a sharp divide over whether the treaty represents a necessary and improved deal or an unnecessary concession of British sovereignty, a dispute that dominated the Second Reading debate.
Voting Aye meant
Support the treaty and Bill, accepting Mauritian sovereignty over the Chagos Archipelago in exchange for a guaranteed 99-year right to operate the strategically vital Diego Garcia base, securing continued UK-US military and intelligence capabilities in the Indian Ocean.
Voting No meant
Oppose the Bill, arguing the deal represents an unnecessary concession of British sovereignty and excessive financial compensation to Mauritius, with critics — primarily Conservatives — contending the government capitulated on a negotiating position inherited from its predecessor.
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 Aye
279
1
81
Conservative and Unionist Party
Whipped No
0
102
14
Liberal Democrats
Whipped No
0
59
12
Labour and Co-operative Party
Whipped Aye
35
0
7
Independent
—
7
3
3
Scottish National Party
—
0
0
9
Reform UK
Whipped No
0
8
0
Sinn Féin
—
0
0
7
Democratic Unionist Party
Whipped No
0
5
0
Green Party of England and Wales
Whipped Aye
3
0
1
Plaid Cymru
—
0
0
4
Social Democratic and Labour Party
—
2
0
0
Your Party
—
2
0
0
Alliance Party of Northern Ireland
—
0
0
1
Restore Britain
—
0
1
0
Speaker
—
0
0
1
Traditional Unionist Voice
—
0
1
0
Ulster Unionist 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 aye · 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 no · 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 no · 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 no · 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 aye · 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 no · 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 no · 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 aye · 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