Keir Starmer’s insistence that handing the Chagos Islands to Mauritius is necessary to secure the long term future of the Diego Garcia military base is facing mounting challenge, after a series of developments that opponents say undercut the Government’s central case.
Labour Ministers have argued that the UK must ratify a UK Mauritius treaty, and pass implementing legislation, in order to remove legal jeopardy and protect a strategically vital UK US facility.
But critics now point to three things the Government cannot easily explain away, a fresh United States contract award that assumes long term continuity at Diego Garcia as British Indian Ocean Territory, a rare United Nations intervention urging suspension of ratification, and an explicit admission in the House of Lords that Mauritius “does not have the capability and expertise” to protect the marine environment Britain has safeguarded for decades.
The dispute centres on the proposed transfer of sovereignty of the British Indian Ocean Territory, including the Chagos Archipelago. Under the treaty, the United Kingdom would pay Mauritius to lease back Diego Garcia for 99 years. Ministers say the deal protects the U.S. / UK base on the largest island Diego Garcia, and reduces the risk of adverse legal rulings and wider litigation affecting operations.
At Third Reading in the House of Lords, the Foreign Office minister Baroness Chapman of Darlington told peers that the treaty “protects the Diego Garcia military base and ensures that the UK retains full control over this vital asset”, and said it was “crucial” that the treaty was ratified “in the ever shifting geopolitical landscape of our age”.
Yet opponents argue that, even on the Government’s own terms, the logic is now strained.
New attention has focused on a United States Department of Defense contracts notice dated 13 January, which announced that Amentum Mitie Pacific LLC had been awarded an $85 million base operating support contract for Navy Support Facility Diego Garcia, with a maximum value of $656 million across options, with work “expected to be completed by January 2034”. The notice describes the location as “Diego Garcia, British Indian Ocean Territory”.
Campaigners say the contract is a straightforward signal of US planning assumptions, namely, that Diego Garcia will remain stable, operable and supported for years, and that the Pentagon is proceeding on the basis of the territory’s current status. Critics argue this sits uneasily with repeated ministerial claims that the base is at risk of becoming inoperable without the sovereignty transfer.
In the Lords, the Government’s case was challenged directly by Conservative peer Lord Lilley, who said ministers had acknowledged that neither the International Court of Justice nor an arbitral tribunal under the UN Convention on the Law of the Sea could produce a ruling “binding on us as to the sovereignty of the Chagos Islands”. He pressed ministers on what he described as a key gap in their argument, asking, “what goods and what services, and supplied by which countries?” He later complained that ministers still had not answered.
The Government’s response, at the close of Third Reading, leaned instead on the practical challenge of sustaining the base. Baroness Chapman told peers, “We rely on other states for supplies, for refuelling and for communications purposes.” She said the issue “needed to be settled”.
Critics, however, argue that reliance on external logistics is not unique to Diego Garcia, and does not explain why the UK must surrender sovereignty and commit to decades of lease payments in order to keep a base functioning that the United States is already funding and supporting.
Alongside the Pentagon contract, opponents point to the Government’s handling of a UN intervention which they say the Government has effectively brushed aside. Peers have cited a decision by the UN Committee on the Elimination of Racial Discrimination, which called for suspension of ratification and raised concerns about the rights of the Chagossian people. In the Lords debate, Lord Callanan described the committee’s stance as “an additional opinion from another UN body”, and criticised what he said was a selective approach to international authority, claiming that one UN view was treated as determinative while another was ignored.
At the same time, environmental concerns have become politically harder to contain, after ministers conceded the scale of Mauritius’s practical limitations.
During Third Reading, Baroness Chapman told peers, “We are working incredibly closely with Mauritius. It does not have the capability and expertise to do this as it stands, but we will make sure that we work alongside Mauritius so that that important work can be done.”
Opponents seized on the line as an admission that Britain would be surrendering sovereign control over one of the world’s most protected marine environments to a state that cannot currently police or manage it without outside help.
The Chagos Archipelago comprises around 60 islands, with Diego Garcia the only island with a significant military presence. For decades, Britain has maintained strict protections over the wider territory, with all but one of the islands uninhabited, home to wildlife and sensitive ecosystems. Critics say the UK’s excellent record of stewardship is a fact, and that the question Parliament must face is whether those protections can realistically be enforced once sovereignty changes hands.
Some peers warned of precisely that risk. Lord Callanan quoted a statement attributed to a Mauritian minister about licensing fishing across the area, and raised doubts about Mauritius’s ability even to reach the territory without assistance, citing reports that Mauritius had sought a vessel to visit and raise its flag.
Others asked why the treaty was not constructed to make UK payments conditional on environmental outcomes. Lord Deben asked Baroness Chapman, “Why on earth was there not a clear connection between our payments and the upkeep of this, the most important marine environment area in the world?” He added, “we have a very proud record on this, yet we are now giving this into the hands of a country which, however good its words, has one of the worst records on marine protection in the entire world.”
A separate strand of concern, repeatedly raised by critics, is the impact of Mauritius’s treaty obligations on military operations. Peers argued that Mauritius is a signatory to the Pelindaba Treaty, which prohibits nuclear weapons on African territory, and warned that transferring sovereignty could invite future legal challenges or political pressure relating to nuclear capable operations, transit, or deterrent posture. Lord Callanan asked how such constraints could be reconciled with ministerial assurances of “continuing unrestricted use” of the base. Baroness Goldie said the flaw was “irremediable”, warning that sovereignty is what currently makes access “unfettered, unchallengeable”.
The Government has insisted that the deal secures the base, and that allies support it. But the combination of the Pentagon’s long horizon contract, the Lords record of ministerial admissions, and the sustained questioning over third party treaty exposure has intensified claims that the Government’s public case is not matching the underlying risks.
The political pressure is increased by the cost to the British taxpayer. Peers referred in debate to a figure of £34.7 billion, with Lord Callanan saying the number had been confirmed, and contrasted it with earlier ministerial descriptions of far lower totals. Lord Altrincham warned that the treaty exposes taxpayers to inflation linked payments over an unusually long period, arguing the sums were “unknown, unknowable and uncapped” over decades.
For opponents, the argument is simple, the Government is asking Parliament to accept a transfer of sovereignty, huge long term payments, and new legal vulnerability, while claiming it is the only way to guarantee the base, even as US planning and spending indicates the base is not poised to collapse without it.
The dispute has also returned focus to the Chagossian people, removed from the islands between 1968 and 1973, and still seeking a secure future and a meaningful voice. Peers noted that Chagossians were watching from the public gallery during the debate. Baroness Hoey called the Government’s approach “hypocrisy” on self determination, and Baroness Foster described a “live judicial review” still awaiting judgment. Lord Hannan said the House should “think again”, warning that the country was “steamrolling over democracy”.
The Bill now goes back to MPs, who will decide whether to accept or overturn Lords amendments. Critics argue the Commons has one remaining chance to stop ratification, and say that, in light of the Pentagon contract and the admissions now on the parliamentary record, the Government’s claim that the treaty is needed to secure Diego Garcia has been overtaken by events.
For ministers, the task will be to explain why surrendering sovereignty and paying for a lease is presented as a security necessity, when the United States is already committing to long term support for Diego Garcia as British Indian Ocean Territory, and when Parliament has been told, in terms, that Mauritius “does not have the capability and expertise” to protect the environment Britain has preserved.
Opponents say MPs should now vote the legislation down, arguing that the deal’s claimed benefits are impossible to substantiate, while its costs, environmental risks, and human consequences are written plainly into the record.
Claire Bullivant
