Diego Garcia Military Base and British Indian Ocean Territory Bill: motion to disagree with Lords Amendment 1

What happened

On 20 January 2026, the House of Commons voted by 344 to 182 to disagree with Lords Amendment 1 to the Diego Garcia Military Base and British Indian Ocean Territory Bill. The vote meant that MPs rejected a modification introduced by the House of Lords and restored the government's original position on the legislation. The Bill concerns a treaty between the United Kingdom and Mauritius governing the future of the Diego Garcia military base in the British Indian Ocean Territory, and the Commons vote was one of several on the same day in which the government overrode a series of Lords amendments to the legislation.

Why it matters

The Bill, if enacted, would give legal effect to a treaty granting Mauritius sovereignty over the Chagos Islands while securing the continued operation of the joint US-UK military base on Diego Garcia for 99 years. The government argues that without the treaty, the legal basis for base operations would be seriously undermined, with potential for court-ordered provisional measures to disrupt access by air and sea and compromise sensitive operations. Rejecting Lords Amendment 1 clears one of the final legislative hurdles before the treaty can come into force, affecting UK national security arrangements, the position of Chagossian communities, and the financial commitments associated with a long-term payment schedule to Mauritius.

The politics

The vote divided almost entirely along party lines, with 334 Labour and Labour Co-operative MPs voting in favour alongside a handful of Independents and smaller party members, while 100 Conservatives, 63 Liberal Democrats, 7 Reform UK members, and 5 Democratic Unionist Party MPs voted against. Just two Labour MPs voted no. The debate was dominated by Conservative interventions citing a statement by US President Donald Trump, made the previous evening, expressing opposition to the deal, which placed the government on the defensive. The government maintained that earlier endorsements from the Trump administration remained the relevant position and that engagement with Washington was continuing.