Overview

• The UK has signed a treaty ceding sovereignty of the Chagos Islands to Mauritius, while leasing back the Diego Garcia military base for 99 years at an annual cost of £101 million.
• The government claims the deal's net present value is £3.4 billion, calculated using standard public-sector discounting practices, but critics argue the nominal cash cost exceeds £30 billion.
• The Conservative opposition has referred Prime Minister Keir Starmer to the UK Statistics Authority, accusing him of statistical misrepresentation and misleading the public on the deal's true cost.
• Critics have highlighted that the United States, a key user of the Diego Garcia base, is not contributing financially to the agreement.
• The treaty, signed on May 21, 2025, now enters a three-week parliamentary scrutiny window under the Constitutional Reform and Governance Act 2010.