The Labour Government is facing mounting accusations that Parliament, and the country, were misled over the legal basis for its decision to transfer sovereignty of the Chagos Islands to Mauritius, after official answers confirmed the UK retains a longstanding opt out from key provisions of international maritime law.
At the centre of the controversy are statements made by the Defence Secretary, John Healey, to the House of Commons on 22 May 2025, the day the UK Mauritius treaty concerning the Chagos Islands was signed and laid before Parliament.
Mr Healey told MPs that without the agreement Britain could face adverse international legal rulings “within weeks”, and that within a few years the strategically vital military base on Diego Garcia could become inoperable. He identified the International Tribunal for the Law of the Sea as the “most proximate, and the most potentially serious” legal threat.
The tribunal adjudicates disputes under the United Nations Convention on the Law of the Sea, UNCLOS. However, Article 298 of the convention permits states to exclude disputes concerning military activities from compulsory binding dispute resolution. The United Kingdom has maintained such an opt out for decades.
House of Commons Video: Labour Defence Secretary John Healey explains why the Treaty is necessary: https://youtu.be/0Q_klwRDf-k
House of Commons Video: James Cleverly asked John Healey what body has jurisdiction to close the base: https://youtu.be/ZzM0yaXK94A
House of Commons Video: Sir Julian Lewis puts Healey on the spot after he ducked James Cleverley’s question. Healey responds with the killer statement: https://youtu.be/PXUVcr0l0s4
In written answers published on 4 and 12 February 2026, the Foreign, Commonwealth and Development Office confirmed that the UK remains party to UNCLOS and continues to rely on its Article 298 exemption, a position unchanged from declarations made in 2003 and 2020. The department also confirmed that the United States was “fully aware” of the UK’s opt out as it applies to the Chagos Islands.
Those confirmations have prompted senior Conservatives to argue that the legal threat described to Parliament in May 2025 could not have resulted in a binding ruling affecting military operations at Diego Garcia.
James Cartlidge, the shadow defence secretary, said the Defence Secretary’s claim that Britain was “weeks away” from losing legal challenges was “simply untrue”. He has written to Mr Healey demanding clarification and calling for the publication of the legal advice underpinning the Government’s position.
In correspondence to the Speaker, Sir Edward Leigh, Sir John Hayes and Sir Julian Lewis have formally asked for the Defence Secretary to return to the House to explain what they describe as an inconsistency between his oral statement and the Government’s subsequent written answers. They argue that the confirmation of the Article 298 exemption undermines the central justification presented to MPs when the treaty was introduced.
The treaty, signed under Prime Minister Sir Keir Starmer, provides for the transfer of sovereignty of the Chagos Islands, formally the British Indian Ocean Territory, to Mauritius, with the UK leasing back Diego Garcia for 99 years at significant cost. Ministers have consistently argued that the deal was necessary to secure the long term future of the base and to resolve ongoing international legal and diplomatic disputes.
Critics now contend that Parliament was asked to scrutinise and later vote on ratification legislation on the basis of an imminent legal threat which, in light of the Government’s own written confirmations, may not have existed in the form described.
The episode has intensified political tensions over the deal and raised wider constitutional questions about ministerial accountability to Parliament. If the Article 298 exemption was operative at the time of the May 2025 statement, opponents argue, MPs were not given a complete account of the United Kingdom’s legal position when being asked to consider one of the most significant sovereignty decisions in recent decades.
The Ministry of Defence has been approached for comment. Ministers have previously maintained that the agreement was reached in the national interest and in response to a complex and evolving legal landscape.
As scrutiny of the legislation continues, the focus is likely to remain on whether the legal risks cited to justify the treaty were accurately characterised, and whether Parliament was fully informed when it was told that the future operability of Diego Garcia was at stake.
LETTER SENT TO SPEAKER OF THE HOUSE:
Images: MOD Crown Copyright News / Editorial Licence.
