More than 40 former British ministers, MPs, peers, military veterans and national security figures have written to former US President Donald Trump urging him to oppose a UK agreement to transfer sovereignty over the British Indian Ocean Territory (BIOT) to Mauritius, warning the move would damage US and UK security interests and could be far more costly than ministers say.
The letter, seen by media outlets on Monday, says the deal reached earlier this year by Prime Minister Sir Keir Starmer to hand the islands to Mauritius while leasing back the US military base on Diego Garcia for 99 years represents a "deliberate act of strategic self-harm," and asks Mr. Trump to use his influence under the 1966 US‑UK defence agreement to oppose the transfer ahead of his state visit to Britain. Signatories include former Conservative leader Sir Iain Duncan Smith, ex-defence secretary Sir Grant Shapps and former home secretary Suella Braverman, alongside a Labour MP, peers, legal experts and national security professionals.
Letter authors warned the transfer could jeopardise operations at Diego Garcia, the strategic US base in the Indian Ocean, by placing the territory under the jurisdiction of a state bound by the Pelindaba Treaty, Africa's nuclear‑weapon‑free‑zone agreement. They said that would create legal ambiguity over the status of US nuclear‑capable forces and could invite inspections, legal disputes or operational restrictions that would erode US deterrence and diminish Western security.
The UK government has estimated the cost of the deal, which includes compensation and financial measures linked to the change of sovereignty, at about £3.4 billion. The TaxPayers' Alliance and some critics say the figure may be much higher, with the campaign group suggesting costs could reach as much as £47 billion if market forecasts for inflation differ from those used by ministers.
Downing Street has said Mr. Trump was informed and "signed off" on the arrangement before it was formally agreed, and that during a conversation in February Mr. Trump told Sir Keir he was "inclined to go with your country" and expected the outcome to be "very well." The letter writers nevertheless appealed directly to Mr. Trump to use both public and private influence to block the transfer, saying: "You have built your reputation on refusing to cede strategic ground to those who would weaken America. We urge you to use your influence, publicly and privately, and your prerogatives under the US‑UK defence agreement of 1966 to oppose this surrender."
Parliament is due to consider a Chagos Bill with a second reading scheduled this week, a parliamentary timetable that critics say is fast‑tracking the change ahead of a judicial review of the deal planned for November. The government says the legislative timetable is necessary to deliver the transfer by the end of the year, as agreed in the settlement with Mauritius.
The dispute follows a protracted legal and diplomatic battle over the future of the Chagos archipelago, which the UK has administered as the British Indian Ocean Territory since the 1960s. Maurice claims sovereignty over the islands; the UK has maintained it held the territory pending a settlement while permitting the US to operate the military installation on Diego Garcia, which has been used for logistics and operations across the Middle East and Indian Ocean region.
Supporters of the transfer argue the arrangement restores sovereignty to Mauritius and secures guarantees for the continued operation of the US base under a long lease, while critics say it risks long‑term access and imposes financial burdens on the British taxpayer. The government has argued the leaseback and legal safeguards will preserve defence cooperation and protect operational continuity on Diego Garcia.
With Mr. Trump preparing for a state visit to the UK in coming weeks and scheduled talks with Prime Minister Sir Keir, the letter represents an attempt by former officials and security figures to influence US involvement in a dispute the signatories say has direct implications for transatlantic defence ties. The outcome of parliamentary proceedings and the forthcoming judicial review will determine whether the transfer proceeds on the timetable set by ministers or is altered by legal challenge.