Navin Ramgoolam says Keir Starmer expressed confidence about finalising agreement within weeks. Downing Street has refused to comment on the prospect of an imminent deal over the Chagos Islands, after the Mauritian prime minister said Keir Starmer had told him he was confident about finalising an agreement in the coming weeks. An interim deal on returning sovereignty of the Chagos Islands to Mauritius, which would maintain the key UK-US military base on the largest of the islands, Diego Garcia, was agreed last year, building on work that began under the Conservative government.

But after Navin Ramgoolam was re-elected as the Mauritian prime minister in November, he demanded to renegotiate the proposals. There has also been a delay to allow for a verdict from the Donald Trump administration in the US. Speaking in the Mauritian national assembly on Tuesday, Ramgoolam said he had discussed the plans with Starmer in a phone call on Friday. “The British prime minister informed me that he intends to push ahead with the agreement reached between Mauritius and the United Kingdom on the Chagos archipelago,” Ramgoolam said. “We remain confident that it will reach a speedy resolution in the coming weeks.”.

Asked about his comments, a Downing Street spokesperson said they would not give “a running commentary on the deal”. He added: “Once an agreement is reached, further details of the treaty will be put before both houses [of parliament] for scrutiny and treaty ratification in the usual way. “I think we have already set out in recent weeks, clearly there is a new US administration in place and as we have previously said it is absolutely right that it has the chance to consider the agreement in full.”.

Under the plan, the UK would lease the military base for 99 years at an annual rate initially estimated to cost about £9bn over the course of the arrangement. However, in his comments on Tuesday, Ramgoolam indicated that the amount could double, as under the revised plan the payments would be linked to inflation. He said: “We have to be inflation-proof. What’s the point of getting money and then having half of it by the end?”.

A UK government source said they did not recognise the idea of the final cost being close to £18bn. The Conservatives have fiercely criticised the plan, despite having begun the negotiations when they were in power. In an official opposition response, the shadow foreign secretary, Priti Patel, said Starmer was “putting his lefty shame of our country’s history over our national security”. The shadow justice secretary, Robert Jenrick, went further, calling Starmer a quisling, an offensive term meaning a traitor or collaborator.