Labour ministers are increasingly concerned President Donald Trump could cancel the deal to cede sovereignty of the Chagos Islands to Mauritius.

The President had previously derided the act as “stupid” and an “act of total weakness”.

In a phone call between Sir Keir Starmer and President Trump, the Prime Minister chose not to mention the treaty, leading to concerns among ministers that the US leader does not understand the deal, reports The Times.

Mr Trump’s British envoy Mark Burnett initially briefed the President on its contents more than a year ago but diplomatic sources said more senior members of the administration had begun to assert themselves.

This includes Treasury Secretary Scott Bessent and US Ambassador in London Warren Stephens, who are among those who have been lobbied by Reform leader Nigel Farage.

Senior Conservatives have suggested their plan is to delay the legislation in the Lords for so long that it fails to pass before the end of the parliamentary session in May.

A Tory amendment calls for the Government to see that the agreement does not breach a 1966 treaty signed with America which confirms UK sovereignty of the islands.

When pressed on if the deal was dead without American backing, a Downing Street spokesman said: “As the public would rightly expect, we’ve negotiated robust security provisions to protect the UK and the base for decades to come.”

Conservative leader Kemi Badenoch confirmed she had discussed the Chagos plan with American politicians, describing it as “a bad deal” for both nations, “long before Nigel Farage went to Davos”.

Despite the mounting concerns, Communities Secretary Steve Reed suggested on Tuesday that the Government believes President Trump may reverse his position.

Mr Reed told Times Radio that the president’s criticism was connected to a dispute with Nato allies over Greenland, from which he has since retreated.

He said: “Donald Trump was saying things a week ago because he was trying to pressure some of his allies to change their position on Greenland sovereignty.”

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Mr Reed added: “We made it clear we’re not going to do that. And now I suspect Donald Trump won’t pursue that point.”

The minister noted that Sir Keir had stood firm against the president’s pressure and that Trump had subsequently withdrawn his threat of tariffs against Britain.

Fresh doubts have emerged over the deal following comments from Paul Berenger, Mauritius’s deputy Prime Minister, who confirmed that nuclear weapons storage would be prohibited at Diego Garcia once the islands are transferred.

His remarks contradict Labour’s assurances that the base would retain “full operational autonomy” under the agreement.

Shadow Foreign Secretary Dame Priti Patel warned the restriction had “serious implications for our security and that of our allies”.

The Policy Exchange think tank has urged ministers to abandon the unratified treaty, cautioning it would “badly prejudice US-UK defence interests.”

Critics highlight Mauritius’s close ties with China and warn the agreement could leave the strategically vital Diego Garcia base vulnerable.

The think tank’s report suggests Mauritius could “accept payments from our adversaries” and permit them access to the archipelago.