Question to the Ministry of Defence:

To ask the Secretary of State for Defence, with reference to page 36 of the Strategic Defence and Security Review 2015, what the costs are of the Successor programme.

As stated in the Strategic Defence and Security Review 15 (Cm9161), our latest estimate of the total cost to manufacture the four Successor submarines is £31 billion; we will also set a contingency of £10 billion. This level of contingency represents about 35% of the costs to completion and is a prudent estimate based on past experience of large, complex projects.

We expect that, once the Successor submarines come into service, the in-service costs of the UK's nuclear deterrent, which include the costs of the Atomic Weapons Establishment, will be similar to those of today - around 6% of the Defence budget.