Nigel Farage has claimed there is “outright hostility” in the US to the UK’s deal with Mauritius to relinquish sovereignty over the Chagos Islands.

The Reform UK leader, who has been a long-time backer of President-elect Donald Trump and visited the US on his re-election, said incoming national security adviser Mike Waltz and defence secretary Pete Hegseth were both opposed to the deal.

The Government announced its decision to relinquish sovereignty over the Chagos Islands to Mauritius last month, which they have argued “saved” a UK-US military base on Diego Garcia.

There is, I can assure you, having been in America last week, knowing also the incoming defence secretary (Pete Hegseth) very well, there is outright hostility to this deal

The agreement over the continued military presence on Diego Garcia is expected to run for 99 years with an option to renew, with Britain paying a regular annual sum of money.

Mr Farage warned the Government against being “at conflict” with the US, without whom the UK would “be defenceless”.

During an urgent question on the Chagos Islands deal, the Reform UK leader told the Commons: “I warned the Foreign Secretary six weeks ago in this chamber that it was an enormous mistake to do this, given that we had a US presidential election coming up on November 5.

“And if you say to me, ‘well, yes, it’s OK, the United States are fully in favour’ – really?

“I can tell you that the incoming national security adviser Mike Waltz has form on this, right back to when (former foreign secretary James Cleverly) was doing his best to give away the sovereignty of the Chagos Islands. Indeed, he wrote to Secretary of State (Antony) Blinken at the time.

“There is, I can assure you, having been in America last week, knowing also the incoming defence secretary (Pete Hegseth) very well, there is outright hostility to this deal.”

He added: “Whatever is said about a lease agreement, as we saw with Hong Kong, these agreements can very, very easily be broken.

“Diego Garcia was described to me by a senior Trump adviser as the most important island on the planet as far as America was concerned.”

Without legal certainty, the base simply cannot operate effectively; continued uncertainty would be a gift to our adversaries. This is why the agreement has been welcomed by all parts of the US system and by other critical regional security partners

Foreign Office minister Stephen Doughty earlier said: “The base on Diego Garcia plays a critical role in countering an array of threats to regional and international security.

“Without legal certainty, the base simply cannot operate effectively; continued uncertainty would be a gift to our adversaries. This is why the agreement has been welcomed by all parts of the US system and by other critical regional security partners including India.”

Shadow foreign secretary Dame Priti Patel said the Government “cannot afford” to “compromise” the UK’s military base on Diego Garcia.

In her first opposition frontbench contribution, Dame Priti said: “The world is a more dangerous place than ever before in our lifetimes, and this Government has agreed to give away a key strategic asset in the Indian Ocean ending more than 200 years of British sovereignty.

“It is a wrong decision, and we stand by that completely.

“A month is now gone since the Government’s announcement, but we’re still in the dark about exactly what the Government has agreed and this is simply not acceptable. We have no treaty and vital questions remain unanswered.

“That is unacceptable, and the minister needs to put that right today. We cannot afford for our military base on Diego Garcia to be compromised in this way.”

The former home secretary also said the Government “rushed into this deal just before the Mauritian elections, even though ministers surely must have realised a change in government was a strong possibility”.

The Prime Minister engaged with the former prime minister of Mauritius, he engaged with the US administration over these matters. We've engaged with a wide range of partners in these discussions ...

Mr Doughty replied: “She will be able to scrutinise these in due course, as will the House, the treaty will be presented the usual way after signature, it will go through the usual process.

“She asks when we’ve, of course, just had the Mauritian election, of course, we will be engaging with the new administration there. We’ll be seeking to present this for signature, and then we will be presenting the treaty in all its detail to the House.”

Mr Cleverly, who initiated negotiations, asked if the Prime Minister had had “any unlimited conversations” with human rights lawyer and chief legal adviser to Mauritius Philippe Sands KC about the Mauritian claim of the Chagos Islands.

Mr Doughty said: “The Prime Minister engaged with the former prime minister of Mauritius, he engaged with the US administration over these matters.

“We’ve engaged with a wide range of partners in these discussions, and he, of course, is very familiar with them, as the former foreign secretary who was part of that process.”

The Chagos Islands have been in British hands for more than 200 years, but after Mauritius gained independence from France in the late 1960s, the inhabitants of the islands were forcibly expelled to make way for the base.

Former Labour leader, now Independent MP Jeremy Corbyn urged the minister not to go down the road of “rebuilding the British Empire, which is apparently what the Conservative Party and Reform want to do”.