2. What assessment he has made of the cost and credibility of a nuclear deterrent based on a cruise missile system. (900041)

A range of cruise missile-based systems were examined as part of the recent Trident alternatives review. The evidence showed that any cruise missile option was more vulnerable and had significantly reduced reach compared with a Trident-based deterrent. Additionally, it would be more costly, requiring the design and development of a new warhead, as well as a new missile.

I am grateful to my right hon. Friend, but will he give me a commitment that in any future negotiations with our coalition partners after the next general election, if by some misfortune no single party should gain an outright majority, our party would retain a continuous-at-sea deterrent with four nuclear submarines?

The Government’s position is that we will maintain continuous-at-sea deterrence, and to do that we are preparing to go ahead at the main-gate decision in 2016 with the delivery of replacement submarines. I fear I would be straying beyond my remit if I were to speculate on negotiations that may or may not take place after the next election.

What is the Secretary of State’s latest estimate of the cost of replacing both the warheads and the submarine system, ahead of the main-gate decision in 2016? Has he given further consideration to the possibility of us not renewing Trident in order to help bring about a nuclear-free world more rapidly rather than re-arming ourselves and thus delaying the possibility of a nuclear-free world?

On the last point, I think that history teaches us that unilateral abandonment of nuclear weapons is not the way to bring about a more rapid elimination of those weapons, much as we would all like to see that happen. I can tell the hon. Gentleman that the estimates produced in the 2006 White Paper for the cost of replacing the existing submarines with a four-boat solution were between £15 billion and £20 billion—in terms of the 2006 economic conditions—and they remain unchanged.

In order that the Secretary of State does not keep having to tell us that he must not go above his pay grade, will he carry the message back to No. 10 that as Labour Front Benchers say they are willing to sign up to two of the four boats before the next election, and as the majority of people in this House would like to have that main-gate decision implemented at least in part, why should we not go ahead so that we cannot be blackmailed by the Liberal Democrats in the event of a hung Parliament after the general election?

I understand my hon. Friend’s point of view. He has on other occasions raised the issue of entering into a contract for the submarines at an early stage. Our current way of managing our equipment programme is to enter into contracts with industry at the point at which projects are mature enough to enable us to secure the best possible value for money for the taxpayer. Entering into a contract at this stage, when the project is relatively immature, would not represent value for money.