[holding answer 12 July 2006]: It is not practicable, except at disproportionate cost, to assess historic expenditure on upgrading or replacing the UK's nuclear deterrent since its inception in the 1950s.
We routinely undertake work to maintain the capability of our existing nuclear deterrent system over its current planned design life. The cost of this work is included within the overall running costs of the Trident system, which have varied between three and 4.5 per cent. of the defence budget since it came into service, up to and including 2005-06.
In terms of expenditure in support of the possible retention by the UK of a nuclear deterrent capability beyond the planned life of the current system, I refer the hon. Gentleman to the answer I gave to the hon. Member for Twickenham (Dr. Cable) on 22 May 2006, Official Report, column 1322W. In addition to the expenditure referred to in that answer, we have previously spent a total of around £9 million.
There is no programme to develop a new United Kingdom nuclear warhead. As was stated in the 1998 Strategic Defence Review, we retain a minimum capability to design and manufacture a new warhead, should one be required. It is not possible precisely to distinguish between expenditure to support retention of that capability and that required to support the current warhead.