Diego Garcia Military Base and British Indian Ocean Territory Bill

Lord Lilley Excerpts

Report stage
Monday 5th January 2026 Lords Chamber

[Baroness Hoey (Non-Afl)]

My Lords, I will refer briefly to my Amendments 17 and 49. I tabled one of them in Committee and want to probe a little further on some of the questions to which I did not get satisfactory answers.

What can we do, how do we know and what can the Government do if a country leases an island ostensibly for a non-security or defence purpose but then gradually introduces security and defence functions from Mauritius? In other words, what power do we have over what Mauritius does to the islands once we have given up our capacity other than for Diego Garcia?

Turning to the deployment of security and defence personnel on islands on the Chagos Archipelago beyond Diego Garcia, what UK approval is required? I have raised this before, but I want to know the detail. Given the announcement on 12 September that India had paid Mauritius to secure a defence presence on a Chagos island, would the Minister please tell the House today whether the Republic of Mauritius asked the UK Government ahead of doing that deal with India? If they did not bother to ask, this provides a good reason for not ratifying the treaty at this stage. If the Republic of Mauritius sought UK approval and it was given, why did the UK Government agree? Surely it was completely inappropriate for the Republic of Mauritius to enter deals on what will happen to the islands in the future when the UK Parliament had not yet agreed to the transfer of sovereignty of the Chagos Islands, as the treaty is still not ratified. Many of us in this place hope that it never will be.

I have no intention of moving my amendments to a vote. I would just welcome the Minister’s response on those two points.

[Lord Lilley (Con)]

My Lords, I apologise to the House for being absent for my amendments in the first group. I am grateful to my noble friend Lord Hannan for moving them on my behalf with, I am sure, greater elegance than I would have been able to bring. Were I a believer in conspiracy theories, I would imagine that President Macron and Prime Minister Starmer had got together to prevent me from returning to this House, but I am sure that they both have more serious issues, given their lack of popularity in their respective countries, than dealing with me.

My Amendment 14 seeks for the Government to negotiate guarantees from the Government of Mauritius that Mauritius will not enforce its duties under the Pelindaba treaty on the base of Diego Garcia and to ensure that, if it were to do so, the sovereignty of the base would revert to the UK. The Pelindaba treaty seems pretty clear that it excludes the use of any part of any African country. Mauritius counts itself as an African country. When it takes sovereignty of the Chagos Archipelago, which we count as part of Africa, it will preclude any of those countries from having any nuclear weapons or armaments on that territory. It would therefore be very difficult, on a simple reading of the Pelindaba treaty, for us to use that for our nuclear submarines or for any aircraft carrying nuclear weapons.

The Mauritius treaty, as it is written, says:

“Each party confirms that none of its existing international obligations or arrangements now in force or effect between it and any third party is in conflict with the provisions of this Agreement”.


If that means that the parties to the agreement intend to ignore any other agreements that they have that may conflict with this, that is all right with me, but the trouble is that it then goes on to say,

“nothing in this Agreement shall affect the status of existing international obligations or arrangements except as expressly provided for in this Agreement”.

That would appear to suggest that nothing in this agreement will override the Pelindaba treaty unless it is expressly stated in this agreement. It is not expressly stated.

I have every confidence in the two Ministers’ patriotism and that they would put the defence of this country manifestly above other minor considerations. I am sure that if it was left to them, we could rely on all this, and I could sit down and not pursue the argument further. But we know that this Government say that their highest priority is international law. If they are now saying that they are prepared to ignore legal agreements and enter into agreements with countries expressly on the basis that they ignore international agreements into which they have entered, we are in a difficult position. I notice the noble and learned Lord, Lord Hermer, is in his place. Perhaps he has come especially to give us assurances that he will not, in this instance, express the supremacy of international law, and that ultimately the sovereignty and independence of this country, its military defence and its alliance with the United States take priority over those matters. Now, if we can have that assurance, that is fine by me.

I appreciate that here we are dealing with very sensitive matters, and I do not expect the Minister to go into fine detail, but I would like the Government to give me greater assurance than I get from reading the treaty that the Pelindaba treaty is not going, at some future stage, to be cited by Mauritius as a reason why we cannot use nuclear-powered vessels or nuclear-equipped weapons, armaments and aircraft from the base. Unless we have that assurance, we must be rather worried.

[The Earl of Leicester (Con)]

My Lords, I, too, was detained in France so I was not able to speak to my first amendment, Amendment 20, but I shall speak to my Amendment 21 and I support all the others in this group. Amendment 21 basically seeks to ensure that the Secretary of State consults the UK’s AUKUS partners on the transfer of the sovereignty of the Diego Garcia base and that we get the written approval of the Governments of Australia and the USA and the opinions of the senior naval staff of all three partners.

AUKUS is central to the strategic defence review. Secretary of State John Healey states in the foreword to the SDR that

“the AUKUS programme … will allow us to grow our nuclear-powered attack submarine fleet to up to 12. This will reinforce our Continuous at Sea Deterrent … and position the UK to deliver the AUKUS partnership with the US and Australia”.

There have been a number of notable naval critics; indeed, one of them, the noble Lord, Admiral Lord West of Spithead, on the Government’s Benches, a former First Sea Lord and Security Minister, warned:

“The Government may genuinely believe that the base’s long-term future is ‘more secure under the agreement than without it’. But … How can the base–which serves as an indispensable naval, air, and intelligence asset–be more secure under the sovereignty of another nation, rather than under our own?”


In November last year, retired Rear-Admiral Chris Parry criticised the Government’s deal to transfer sovereignty of the Chagos to Mauritius. He described the decision as “the biggest strategic mistake” he has seen in his lifetime. In February last year, Commander Peters, a retired Royal Navy officer who led British forces at the joint UK-US base on Diego Garcia said that the base was currently “easily defended”, but:

“If the outer islands are under Mauritian control, China could quite happily start redeveloping them and installing all sorts of spying equipment that I think would affect the security of Diego Garcia”.

--- Later in debate ---

Moved by

[Lord Lilley]

10: Clause 1, page 1, line 7, at end insert
“, subject to subsection (2A).
(2A) Sections 2 to 4 of this Act come into force only when either the International Court of Justice or the International Tribunal for the Law of the Sea has delivered binding and enforceable judgements on the sovereignty of the Chagos Archipelago and judged that the islands should be transferred to Mauritius.” Member’s explanatory statement
This amendment would only allow sections 2 to 4 to come into force if an international Court delivers a binding ruling on sovereignty of the Chagos Archipelago and directs that they should be transferred to Mauritius.

[Lord Lilley (Con)]

My Lords, I will very briefly talk to my Amendments 10 and 15. When any Administration shift from the original arguments which justified their policy to a new set of arguments, you know that they are moving from evidence-based policy to policy-based evidence. That seems to be what is happening here.

When the original Statement was made about this treaty on 22 May, the Defence Minister in the other place said that if we did not have this treaty, within weeks we would face a binding legal judgment which would in due course render the base inoperable. That was implicitly based on the case before the International Court of Justice, but no mention was made that that ruling was purely advisory, not binding. No mention was made that it was based on General Assembly resolutions, which themselves are not binding and had never been ratified by the Security Council, where, in any case, we have a veto. There was no mention that when we signed up to the ICJ, we specifically precluded it from hearing or being bound by anything relating to disputes between the UK and Commonwealth members, and that subsequently, in 2012, the Cameron Government had tightened that by saying it should be not just present Commonwealth members but present or past Commonwealth members, just in case Mauritius should leave the Commonwealth to pursue its case.

When we mentioned these things, the Government did not say, “Oh yes, you’re quite right: we should have mentioned this earlier”. They simply shifted to talking about the possibility of tribunals in other fora, above all the UN Convention on the Law of the Sea—but that convention cannot address sovereignty. In Committee, the Minister mentioned that in a dispute between Mauritius and the Maldives, in which Britain was not represented, the tribunal assumed on the basis of the ICJ treaty that the boundaries of Mauritius should include Chagos and ruled on that basis. But we have the right in any future dispute that involves us to be represented; above all, we have the right to invoke, I think, amendment 238, which precludes military matters. The Diego Garcia base is above all a military matter. So I do not see where any binding legal judgment could come from, which is why I say that this should not come into force until we see that there is a binding ruling from some international body. If it is going to happen within weeks, that is not going to delay the whole matter very much.

The second issue, which is dealt with in my second amendment, is the reference to any ruling—by whichever international body it is—effectively rendering the base inoperable. When we press on that, we are told that it would mean that countries that supply the base and provide facilities for the base would be able to withdraw those facilities, which in some way would render it inoperable. As to what these facilities are, I presume they get food from neighbouring countries in boats—but nothing much has changed. If countries wished effectively to impose an embargo on the Diego Garcia base, with or without an international resolution from the ICJ or any other tribunal, they could do so. If that would render the base inoperable, the base is much weaker than we thought; and, if they cannot do so, surely there is nothing much to worry about on whether there is a legal ruling.

I do not want to go on at length because I know that noble Lords want to get on to the important business of expressing their views in the Lobbies. But the fundamental basis of this whole treaty has shifted, like the Goodwin Sands—and, like sinking sands everywhere, when they shift, they swallow you up. The Government’s rationale for this whole Bill has been swallowed up by their refusal to just wait and see whether some tribunal would come up with some ruling which would, in some very strange way, render the base inoperable. I find that imaginary but, if it is possible, let us suck it and see.

[Baroness Chapman of Darlington (Lab)]

We have been through this quite a few times, which I suppose is why other noble Lords are not jumping to their feet. Why not wait for a binding ruling? We have discussed previously that that would leave us in a disadvantaged position in terms of negotiation, were we to be negotiating with Mauritius following a binding ruling. The point that there can never be a binding ruling because no tribunal exists that could make one rather begs the question of why the previous Government committed themselves to 11 rounds of negotiations to protect themselves from something that could never happen.

Having said all that, the amendments tabled by the noble Lord, Lord Lilley, concern the legal rationale and the risks of the agreement, including, in Amendment 10, waiting for a binding ruling on sovereignty over the archipelago. I must again reject this argument and this amendment, given that waiting for such a thing, with the treaty with Mauritius not ratified, would put us in an incredibly weak position. It would risk the future of the base, the delay would be highly dangerous to UK national security, and we are just not going to do it.

We published our legal rationale for the deal on the day that the treaty was signed. The House has dedicated hours to debating that rationale. It has been the subject of two reports by respected committees in this place. The Government have been consistently clear throughout all this that the legal case was compelling and there was no credible alternative for managing the risk, which is why the previous Government undertook so many rounds of negotiation. We are confident that this agreement secures the base from legal threat, protecting UK national security for generations. I hope the noble Lord does not press his amendments to a vote.

[Lord Callanan (Con)]

My Lords, the argument that the treaty was necessary because of the advisory judgment of international courts is something that we have debated at length. But, as my noble friend Lord Lilley has consistently demonstrated, the reality is that the Government had a political choice and they could have not entered into the agreement. In the meantime, though, as the hour is getting late, it remains only for me to say that, if my noble friend presses his amendment to a vote, we will support him. Sorry, I spoke in the wrong place there.

[Lord Lilley (Con)]

My Lords, I am grateful to the Minister for responding to my points. I still do not think she has explained why a delay would weaken our negotiating position when that position has been based on the fact that we would face a binding ruling. If that happens, our negotiating position is no worse, and if it does not happen, it is much stronger. Still, I do not want to cause a vote if that is going to delay more important votes where we might win.

Amendment 10 withdrawn.