Diego Garcia Military Base and British Indian Ocean Territory Bill: motion to disagree with Lords Amendment 5

Parliament voted on 20 January 2026 to reject Lords Amendment 5 to the Diego Garcia Military Base and British Indian Ocean Territory Bill. The amendment, passed by the House of Lords, would have required the Secretary of State to publish the total real-terms costs of payments made under the treaty, including the methodology used by the Government Actuary's Department and the Treasury. The House of Commons voted to disagree with that amendment by 347 votes to 185, meaning the Lords' proposed change was removed from the Bill.

The practical effect of the vote was to maintain the government's position that existing published documents, including the financial exchange of letters and the explanatory memorandum laid before Parliament at the time of signature, provide sufficient transparency about the treaty's costs. The deal commits the United Kingdom to payments to Mauritius in exchange for a long-term agreement on Diego Garcia, a strategically vital joint US-UK military base in the Indian Ocean. The government argued the financial details had already been verified by the Government Actuary's Department, the House of Commons Library, the Office for Statistics Regulation and the Office for Budget Responsibility, making the Lords amendment duplicative rather than adding genuine accountability.

The vote divided almost entirely along government-versus-opposition lines. Labour MPs (including Labour and Co-operative members) voted overwhelmingly in favour of rejecting the Lords amendment, providing the government's majority. Conservatives, Liberal Democrats, Reform UK, the Democratic Unionist Party and Plaid Cymru voted against. Three Green MPs voted with the government. The debate took place against an unusually turbulent backdrop: President Trump had publicly expressed hostility to the deal the previous night, prompting repeated challenges from opposition MPs who argued that circumstances had materially changed.