David Lammy was heckled in the House of Commons as he defended the decision to give up UK control over the Chagos Islands.

The Foreign Secretary said the UK Government wants the treaty with Mauritius signed and ratified in 2025, arguing it is a “historic moment” which has “saved” the joint UK-US military base on Diego Garcia, the largest of the islands.

He added the deal with Mauritius “does not signal any change in policy to Britain’s other overseas territories”, amid concerns over the possible ramifications on the Falkland Islands and Gibraltar.

But Mr Lammy faced angry scenes in the Commons, with those on the Conservative benches in particular heckling and shouting at the Foreign Secretary as he delivered his statement and answered questions.

Conservative Party leadership hopeful Tom Tugendhat repeatedly shouted “not true” as Mr Lammy set out the reasons behind the Government’s decision to relinquish sovereignty over the Chagos Islands, also known as the British Indian Ocean Territory (BIOT).

Mr Lammy told the Commons: “Since its creation, the territory and the joint UK-US military base on Diego Garcia has had a contested existence. In recent years, the threat has risen significantly.

“Coming into office, the status quo was clearly not sustainable. A binding judgment against the UK seemed inevitable and it was just a matter of time before our only choices would’ve been abandoning the base altogether or breaking international law.”

Mr Lammy highlighted support from the United States for the deal and said Mauritius would be free to implement a resettlement programme to islands other than Diego Garcia.

This is a historic moment, a victory for diplomacy. We saved the base. We secured Britain’s national interest for the long term

Turning to concerns over the impact of the agreement on other British overseas territories, Mr Lammy said: “I want to reassure the House and all members of the UK family worldwide that this agreement does not signal any change in policy to Britain’s other overseas territories.

“British sovereignty on the Falkland Islands, Gibraltar and the sovereign base areas, is not up for negotiation. The situations are not comparable. This has been acknowledged across our overseas territories.”

He added: “The Government remains firmly committed to modern partnerships with our overseas territories based on mutual consent.

“After Mauritius’ elections, the Government will move towards treaty signature, and it is then our intention to pursue ratification in 2025 by submitting the treaty and the Bill to this House for scrutiny.

“This is a historic moment, a victory for diplomacy. We saved the base. We secured Britain’s national interest for the long term.”

By this statement today, the Government gives succour to our enemies in a dangerous world

Shadow foreign secretary Andrew Mitchell said that neither of Mr Lammy’s Conservative predecessors – Lord Cameron or James Cleverly – would have agreed the deal, despite the 11 rounds of negotiations involving the Foreign Office under the previous Tory administration since 2022.

He sought clarity on how Mr Lammy has reassured the people of Gibraltar and Falkland Islands that the “ill-advised decision will have no effect on their sovereignty”.

Mr Mitchell also said: “By this statement today, the Government gives succour to our enemies in a dangerous world, and undermines the strategic web of Britain’s defence interests. Mr Speaker, our country is the poorer and the less for it.”

Liberal Democrat foreign affairs spokesman Calum Miller said there has been “no opportunity” for the Chagossians to have the right to self-determination and said their voices must be “injected” into the process.

He went on to express concern over some of the language used by Tory MPs, saying: “There is no equivalence between the Chagos Islands and other British overseas territories. We must be absolutely clear about that.”

Conservative MP Andrew Rosindell (Romford) said: “This is a shameful day for British democracy. This is a dark moment for human rights in the United Kingdom.

“Already the people of the Chagos Islands have been forcibly removed from their homeland, today this Government is handing their home over to a foreign country in cahoots with a hostile nation.”

Tory former leader Sir Iain Duncan Smith said he was opposed to his party’s negotiations while in government before he raised concerns over the conduct of the “disgusting” Mauritian government, who he claimed are “in league with the Chinese”.

Mr Lammy said Mauritius is part of the Commonwealth, adding: “I can’t possibly associate myself with the remarks he just made.”

The United Nations’ highest court, the International Court of Justice, previously ruled the UK’s administration of the territory was “unlawful” and must end.

Ahead of Mr Lammy’s statement, Downing Street said the deal to give up sovereignty over the BIOT was because of the “unsustainable” legal position and had no impact on other sovereignty disputes.

Reform UK leader Nigel Farage said: “It would appear the potential next judgment of a spurious, rather political, foreign court matters more than the issue of national sovereignty.”

He asked how confident Mr Lammy would be over Donald Trump supporting the deal if the Republican candidate wins next month’s US presidential election.

Commons Speaker Sir Lindsay Hoyle earlier admonished the Government for making the announcement during recess when the House was not sitting, describing the situation as “frustrating”.

The agreement over the continued UK-US 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.

Chagossians were forced to leave the central Indian Ocean territory by 1973 to make way for the military base.

The expulsions are regarded as one of the most shameful parts of Britain’s modern colonial history and Chagossians have spent decades fighting to return to the islands.