16. What estimate he has made of the minimum number of submarines required to maintain a continuous-at-sea nuclear deterrent. (159650)

17. What assessment he has made of the potential effect that a reduced number of nuclear-armed submarines would have on the UK’s ability to maintain a continuous-at-sea deterrent. (159651)

The 2006 White Paper, “The Future of the United Kingdom’s Nuclear Deterrent”, stated that the minimum number of Vanguard class submarines required to maintain a continuous-at-sea nuclear deterrent was four. The number of submarines required to deliver CASD into the future will be determined in the main gate investment decision for the successor replacement for the Vanguard class, which is expected in 2016. This is a technical, rather than a policy, question.

Has my right hon. Friend seen recent media reports that the Liberal Democrats might be proposing a reduction to just two nuclear submarines? Does he agree that it would be impossible to maintain a continuous-at-sea deterrent, which is the hallmark of national security?

I have learned not to read too much into newspaper reports. The main gate decision in 2016, which will define the number of submarines required to maintain CASD, will consider the case for four or three submarines, but I can say without equivocation that there is no possibility of maintaining CASD with two submarines.

Does my right hon. Friend agree that any cost savings from a proposal to reduce the UK’s fleet of ballistic missile submarines to just two would need to take into account the requirement to maintain the UK’s sovereign submarine manufacturing capability?

My hon. Friend is absolutely right. Simply reducing the fleet, even if that were possible while maintaining CASD, would not generate proportionate savings. Many of the costs are fixed—the costs of development and maintaining industrial capability, not merely at Barrow-in-Furness for submarine building, but in the nuclear propulsion industry. No one in this House should ever forget either that these high-end, high-technology platforms support the very top end of British manufacturing industry—the high-precision, high-technology engineering industry on which the revival of manufacturing depends.

Will the Trident alternative review be published as a Government document or a Liberal Democrat document?

An unclassified summary of the Trident alternative review will be prepared by the Cabinet Office and published as a Government document.

In January, the Chief Secretary to the Treasury told The Guardian newspaper that the coalition review of Trident would compile a “compelling” list of alternatives. It was suggested in the Financial Times recently that the review will come down on the side of a submarine-based ballistic missile system. In the light of that, will the Secretary of State tell the House when the review will be published, and if it comes down on the side of a submarine-based system, will the Government consider bringing forward the main gate decision into this Parliament?

I cannot comment on the findings of the review, which is not yet concluded and has not yet reported to the Prime Minister and the Deputy Prime Minister, but I can tell the hon. Gentleman that there is no need to bring forward the 2016 main gate decision point. That decision will be made in 2016, in order to deliver the new submarines into service from 2028, when they are required.

I wonder whether the Secretary of State has responded to Rear-Admiral Patrick Middleton, who wrote in The Times on 7 May:

“With the latest developments in defence technology, the argument for Trident as a deterrent is rapidly becoming a losing one”.

I am afraid I do not agree with him. I suspect this is a retired rear admiral—well, I know it is; and if it isn’t, he soon will be—to whom the hon. Lady refers. We are clear that the retention of the continuous-at-sea deterrent is vital to ensure Britain’s national security and is the ultimate guarantee of our sovereignty.

I very much look forward to welcoming the Minister for defence equipment, the Under-Secretary of State for Defence, the hon. Member for Ludlow (Mr Dunne), and the shadow Secretary of State to my parliamentary reception on 1 July about the high-end manufacturing jobs that the submarine supply chain produces. The durability of the submarine hulls is critical to the decisions and the timing of renewal. Will the Secretary of State give the House an update on his Department’s assessment of extending the hull life to 35 years, as is currently the case, and any possible decision to extend it further in future?

First, I will check my diary. I thank the hon. Gentleman for his kind invitation.

I am not sure whether the hon. Gentleman is asking if we have considered whether it is possible to extend further the life of the existing submarines or to design the successor class with a longer in-service life. On the first question, he will know that we have already extended the life of the Vanguard class once, and it is not judged possible or safe to extend it further. On the second question, we will of course be looking to design the successor class with the longest possible in-service life.

My right hon. Friend is clearly very robust on this issue, but may I urge him to consider deeply the suggestion of the shadow Armed Forces Minister, the hon. Member for North Durham (Mr Jones)? If those on both Front Benches agree on the need to renew Trident and to keep continuous-at-sea deterrence, why should they not agree before the general election to make this irreversible, so that Trident cannot again become a political football, as it unfortunately did between my party and the Liberal Democrats in 2010?

I have to say to my hon. Friend—who is a great expert on this subject and has been one for longer than I can remember—that the essence of our strategy for defence procurement, which is at the heart of our determination to maintain a balanced budget, is that we do not make contractual commitments until we need to for the delivery of equipment in a timely fashion, when we need it. Locking in decisions before they need to be made merely reduces flexibility and, as the previous Government found out, drives cost into the programme if changes have to be made.

The hon. Member for New Forest East (Dr Lewis) has spoken eloquently at me on the matter for 30 years.