The Defence Secretary has placed decolonisation at the origin of the legal dispute over the Chagos Islands, at the moment the security case for the treaty that would settle it is under renewed pressure from Washington.
Asked on Wednesday whether the archipelago would still be handed to Mauritius, Wes Streeting did not contest the point. “That’s not really been in doubt,” he told Sky News. “Where the legal dispute on this started was when we decolonised.”
That is a precise answer, and it matters. Successive British governments have argued the case for the treaty on security grounds: that only a settlement with Mauritius could guarantee the future of Diego Garcia, the joint UK and US base that has supported American bombing runs across the Middle East, and secure it for 99 years. When Sir Keir Starmer signed the treaty in May 2025 he called it “absolutely vital” for the “safety and security of the British people”, and his government set out its legal reasoning in detail in a published statement.
Streeting’s answer puts decolonisation explicitly into the British government’s explanation of how the dispute arose. Mauritius has long described the settlement in those terms. Its prime minister, Navin Ramgoolam, said after the treaty was signed that “we have gained recognition of our sovereignty over the entire archipelago of Chagos, including Diego Garcia, which completes the process of decolonisation which began in 1968”, as recorded in the House of Commons Library briefing on the agreement.
The International Court of Justice reached its conclusions on the same ground. In its advisory opinion of 25 February 2019, the court found that the process of decolonisation of Mauritius was not lawfully completed when the country acceded to independence in 1968, and that the United Kingdom was under an obligation to bring its administration of the archipelago to an end as rapidly as possible. The opinion is authoritative but not a binding judgment between the two states. The UN General Assembly endorsed it in Resolution 73/295 four months later, and the tribunal the UK’s own legal assessment treats as the greater risk, a Special Chamber of the International Tribunal for the Law of the Sea, ruled in 2021 that Mauritian sovereignty could be inferred from it.
An unidentified opinion
Streeting also referred to legal advice that has not been published. Ministers did not want to “take a risk on such a sensitive defence asset”, he said, adding: “There’s a legal opinion, and it’s a draft opinion for now.”
No minister has identified the document. The ICJ’s 2019 opinion was delivered in full and final form, and is therefore a different piece of work. The Government’s published legal position rests on the risk of future binding litigation, not on any draft still in circulation.
“Not good enough”
The Defence Secretary was speaking the morning after the treaty’s most serious setback. In his first face to face meeting with the Prime Minister, Andy Burnham, on the margins of the UN General Assembly, President Trump said he did not support the agreement. “I think it’s terrible. It was a terrible deal,” he told The Telegraph. “Strategically it’s very important… I think the Prime Minister is going to be looking at it.” According to the Telegraph’s account, Burnham nodded.
By Wednesday morning Streeting had accepted the conclusion, telling Sky News: “Objectively, in the absence of support from the Americans, is this deal good enough? No. It needs to have the support of the Americans.” On the BBC’s Today programme he said it again: “This deal as it is currently constituted can’t go ahead without American support. So we have to get a deal to a place where it commands American support as well as the agreement of the government of Mauritius and our government.”
He did not resile from his own record. “I was a member of the Cabinet that agreed the deal with the government of Mauritius, and I stand by the decision that was taken then,” he said, adding that the principle throughout had been that the agreement needed American support. He said Britain would not pay Mauritius £120m a year “at this stage”, and described the sum as a small fraction of the overall defence budget.
What Britain pays
The payment structure is set out in the treaty documents laid before Parliament. Britain is due to pay £165m a year for the first three years, and £120m a year for the following ten. For the remaining 86 years the payment is the equivalent of £120m a year in today’s prices, rising with inflation. Two other commitments sit alongside the lease payments: a one off £40m payment in year two to capitalise a trust fund for Chagossians, and £45m a year for 25 years from year four for development projects in Mauritius.
Two figures are used for the whole agreement, and they measure different things. Government Actuary’s Department projections obtained by the Conservatives in August 2025 put the projected nominal cash payments at £34.7bn. The Government instead expresses the cost as £3.4bn in net present value terms, an average of £101m a year in 2025/26 prices, discounted using the Social Time Preference Rate. Full Fact reports that both are technically correct and that the Treasury and the Institute for Fiscal Studies regard the lower figure as the more useful way of expressing the scale of a 99 year commitment, while noting that the discount rates involved have been in use since 2003.
Where the treaty came from
The treaty did not begin under this government. Negotiations opened in November 2022 under the previous Conservative administration, which held 11 of the 13 rounds of talks, as the Commons Library records. The treaty itself was signed on 22 May 2025.
Ratification has been stalled since January, when the Government postponed a House of Lords debate on the bill giving the treaty effect in domestic law, after Conservative peers tabled an amendment calling for a pause “in light of the changing geopolitical circumstances”. The bill remains unpassed and the treaty unratified, and the Government has said ratification also requires an updated 1966 UK-US agreement on the base, whose first clause states that the territory “shall remain under United Kingdom sovereignty”. Chatham House has argued that clause was drafted to reassure Britain that it retained sovereignty despite the basing rights granted to the Americans, and that it does not amount to an undertaking of permanent British sovereignty. The Lords amendment did not itself kill the treaty. It deferred its passage.
President Trump’s own position has moved more than once, and not always in the same direction. He was recorded early in his second term as inclined to go along with the agreement, and the US said after an interagency review that it secured the stable operation of the base. He then attacked it on 20 January, calling it an “act of great stupidity”, before appearing to signal approval again ten days later, with the qualification that the US would retain the right to reinforce its presence on Diego Garcia if it came under threat. He came out against the deal once more on 10 February, after Britain declined a request to use the base for strikes on Iran. On Tuesday he returned to that grievance, telling reporters: “We had to send the B-2 bombers back home to Missouri.”
Burnham changes course after Trump meeting
On Monday the Prime Minister told Ramgoolam he would “reiterate his commitment to continue doing everything possible, together with the USA, towards the ratification of the Chagos treaty”, according to the Downing Street readout of their call. On Tuesday he met Trump. Afterwards, he said he had “inherited the situation” and that “we need a resolution”, and he did not deny suggestions that the deal was dead or would change.
Kemi Badenoch, the Conservative leader, said: “In the space of 24 hours, Andy Burnham managed to have three positions on the Chagos Islands. Rather than these silly contortions, he should just scrap this terrible deal.” James Cartlidge, the shadow defence secretary, said the deal should be “binned entirely”, calling it absurd “to hand over British sovereign territory, not to mention billions of pounds of hard-pressed taxpayers’ money, to an ally of China”.
The pressure is not confined to the opposition. Lord Kinnock, the former Labour leader, told Sky News that Burnham was “right to review” the agreement and that it was “exactly the right place to put himself”. Lord Glasman, who founded the Blue Labour group, told The Telegraph: “I have never understood this deal from the start. It’s an overhang of Hermer’s extremist human rights agenda.” Dan Carden, a former shadow minister, told politics.co.uk that dropping the policy could protect other overseas territories, naming the Falklands, and added: “I have some hope that he will look at the disastrous Chagos deal and drop it.” Nigel Farage had lobbied the US government on Chagos in the week before the meeting, and a source close to the Reform UK leader said his “high level” conversations had “paid off”.
Sir Keir Starmer’s government presented the treaty as the only route to securing Diego Garcia and ending a dispute it said Britain would not win in court. Burnham’s government is now reviewing that agreement, and says it is looking for a resolution.
The UN Committee on the Elimination of Racial Discrimination raised the same question in December, in a decision issued under its early warning and urgent action procedure. The committee said it was deeply concerned that the agreement would perpetuate longstanding violations of the Chagossian people’s rights, and that the lack of meaningful participation of Chagossians was “affecting their rights and lands” and “restricting the exercise of their right to self-determination”. It called on both the United Kingdom and Mauritius to suspend ratification and to engage immediately in a renewed dialogue to ensure the free, prior and informed consent of the Chagossian people. The decision is not a court judgment and does not bind either government.
Claire Bullivant, of the Great British PAC, said:
“This is an extraordinary admission from Wes Streeting. For over a year this deal has been sold to the British public as necessary to secure the future of Diego Garcia. Now a Labour Defence Secretary is openly describing it as ‘decolonisation’, while simultaneously admitting that the agreement cannot go ahead in its present form without American support.
“But there is one group Labour still seems determined not to listen to, the Chagossian people themselves.
“At the Great British PAC we have been working directly with Chagossians, supporting and funding their legal fight, commissioning substantial polling and maintaining contact with thousands of members of the Chagossian community. What we hear overwhelmingly is that they want their voices heard and they want to remain British.
“The United Nations Committee on the Elimination of Racial Discrimination has already called on Britain and Mauritius to suspend ratification of this treaty, expressed grave concern about the lack of consultation with Chagossians, and said their free, prior and informed consent must be secured.
“President Trump has now called the agreement a ‘terrible deal’, the United States will not support it in its present form, and Labour itself admits it cannot proceed as drafted.
“So why is the Government still treating the wishes of the Chagossian people as an afterthought? If Labour genuinely believes this is about decolonisation and self-determination, then surely self-determination must begin with asking the Chagossians themselves.
“They are not pieces on a diplomatic chessboard. These are their islands, their heritage and their future. They want to return to their homeland as British citizens. It is time the Labour Government listened to them.”
The treaty was presented by ministers as the way to secure Diego Garcia for another 99 years. Streeting has now put the legal dispute behind it explicitly back where it began: decolonisation. With Washington withholding its support and the Government reviewing the agreement, both arguments are now being tested at once.
