Former US President Donald Trump has launched a blistering public attack on Prime Minister Sir Keir Starmer, condemning the UK's agreement to cede sovereignty of the Chagos Islands to Mauritius as an act of "great stupidity" and "total weakness".
A Deal Under Fire and a Surprising U-Turn
The extraordinary criticism, posted on Mr Trump's Truth Social platform on Tuesday 20 January 2026, directly targets the treaty signed in May 2025. This agreement will see the British Indian Ocean Territory, which includes the strategically vital UK-US military base on Diego Garcia, transferred to Mauritius. The UK government, however, has negotiated to pay billions to lease back the base, securing its operations for the future.
The attack has caught Number 10 off guard, particularly as Mr Trump had previously welcomed the same deal as a "monumental achievement" that secured the long-term future of the Diego Garcia facility. His latest remarks represent a stark reversal and come as legislation to implement the treaty faces a difficult passage through the House of Lords.
The Stakes: Security, Sovereignty and Billions
Ministers have defended the controversial agreement, arguing it was necessary after international court rulings, including a 2019 advisory opinion from the International Court of Justice, undermined the UK's legal position and threatened the future operation of the base. The financial terms are substantial: the UK has established a £40 million fund for displaced Chagossians and has agreed to pay Mauritius at least £120 million annually for 99 years. In nominal terms, this could see the total cost reach approximately £35 billion.
In his post, Mr Trump framed the decision as a grave strategic error, stating: "There is no doubt that China and Russia have noticed this act of total weakness." He even linked it to his own geopolitical ambitions, citing it as a reason for pursuing the acquisition of Greenland.
Political Fallout and a Defence of the Deal
The intervention has been eagerly seized upon by opponents of the agreement in the UK. Conservative leader Kemi Badenoch stated the policy "weakens UK security and hands away our sovereign territory," while Reform UK's Nigel Farage claimed Mr Trump had "vetoed the surrender".
The UK Government has issued a robust defence. A spokesman emphasised that the deal was struck to protect the Diego Garcia base from legal challenges that would have prevented its future operation. They noted it "secures the operations of the joint US-UK base on Diego Garcia for generations" and has been welcomed by the US, Australia, all other Five Eyes allies, and partners including India and Japan.
As the Commons prepares to consider amendments from the Lords, Mr Trump's unexpected broadside has cast a long shadow over the final parliamentary stages of this high-stakes diplomatic and defence arrangement.
