Diego Garcia Military Base and British Indian Ocean Territory Bill

Key Points

• Implements the UK–Mauritius treaty on Diego Garcia and the British Indian Ocean Territory (BIOT), including potential changes to BIOT’s constitutional status and nationality rules for people connected with BIOT.
• Lords amendments seek wide safeguards: recognise Chagossian rights (including potential return and a referendum on sovereignty), require negotiations with Mauritius on resettlement and asylum, and establish robust governance and reporting (including a Joint UK–Mauritius Parliamentary Commission and an inter-parliamentary committee).
• Provides for cost transparency and financial accountability, including parliamentary scrutiny of treaty payments to Mauritius and mechanisms to delay or condition parts of the Act pending environmental protections and other safeguards.
• Introduces procedural controls on Orders made under the Act (notably Clause 6), including a push for negative resolution scrutiny, and contemplates additional safeguards such as independent reporting on environmental and legal risks before provisions take effect.
• Evolution of the bill shows a sharp policy debate: Lords pressed for extensive protections and rights for Chagossians and for tighter parliamentary oversight, while the Commons has rejected many of those provisions and moved to maintain the original treaty framework; on 20 January 2026 the Commons voted to disagree with several Lords amendments.
• Key policy tensions include sovereignty versus decolonisation/return rights for Chagossians, the level of parliamentary control over treaty payments and orders, environmental protections for the BIOT Marine Protected Area, and the sequencing of when different provisions come into force.

Progress

The bill began in the Commons and moved to the Lords, where a large package of amendments was proposed. The Commons subsequently disagreed with several Lords amendments, and the bill is currently in the Lords to resolve those differences and determine the final form.

Voting

In late January 2026, the Commons voted to disagree with Lords Amendments 1, 5 and 6, reflecting government and many MPs’ preference to keep the treaty terms closer to the Commons’ original plan. Across parties, there was a mix of support and opposition to different amendments, with Labour and many Conservatives backing the government line, while Liberal Democrats and some smaller groups tended to oppose some of the Lords’ safeguards.