Donald Trump may end up having the final say in the UK’s plan to hand the Chagos islands over to Mauritius.

Keir Starmer’s spokesperson told journalists today it would be “perfectly reasonable” for the incoming US administration to have a look at the agreement before it passes.

The deal would see the UK maintain a 99-year lease over the joint UK-US military airbase on the largest island Diego Garcia, while the archipelago’s sovereignty would pass to Mauritius.

Ministers had hoped to get the agreement signed off before Trump takes office, amid reports that he does not support it.

Despite reports the deal would be signed off on Wednesday, Mauritius has not yet accepted the UK’s proposals and the country’s attorney general is returning to London for more talks.

That means the issue will still not be across the line before the president-elect’s inauguration in five days’ time.

While denying that Trump is effectively being given a “veto” on the policy, a spokesperson for the prime minister said it was “perfectly reasonable for the US administration to consider the detail” of any agreement.

Trump’s top team has already expressed doubt over the plan, with the incoming US secretary of state Marco Rubio saying the deal poses a “serious threat” to American security.

Mauritius has been independent from the UK since 1968 and the UN previously ruled that the UK’s administration of the archipelago is “unlawful”.

It was actually the former Tory government which started the process of handing over Chagos, but Tory leader Kemi Badenoch still criticised the PM over it during Wednesday’s PMQs.

She accused the PM of “negotiating a secret deal to surrender British territory and taxpayers in this country will pay for the humiliation”.

She added that there was “no way we should be giving up British territory in Chagos” and said Labour was “rushing a deal which will be disastrous”.

The PM defended the move saying it was the most effective way to protect the territory.

The shadow foreign secretary Priti Patel said: “This is a complete humiliation for Keir Starmer and [foreign secretary] David Lammy and marks yet another failure of British diplomacy under Labour.

“Labour have been desperate to sign off the surrender of the Chagos Islands before President Trump returns to office, and the Mauritius government know.

“They see the weakness at the heart of this government and are trying to exploit it by pressuring Britain into paying more for an even weaker lease for the military base at Diego Garcia.”

“While Labour have been hiding the details from us, we know they are prepared to blow billions of pounds of taxpayers’ money for the indignity of this dodgy deal, which will undermine our security and defence.

“It is high time they abandoned it altogether start focusing on how to strengthen our defence capabilities and get the economy growing.”