In its recent Strategic Defence Review Labour said Britain's "nuclear warhead programme as a whole" cost pounds 410m, but anti-nuclear campaigners claim the true cost to the taxpayer is as high as pounds 1.5bn.
The gaping difference has been exposed by the Campaign for Nuclear Disarmament in the type of exercise it used to carry out for Labour MPs when they were in opposition.
William Peden, CND's Parliamentary researcher, said: "Labour are quite clearly embarrassed to have inherited Trident yet done nothing to get rid of it, so they have decided instead to make it look inexpensive. They have missed out whole tranches of expenditure."
The Ministry of Defence last night dismissed the claims, saying the costs were clearly published within the review. However, CND said they had been presented to voters in a less than transparent format.
In the review, the cost of the Trident nuclear submarine is put at pounds 114m and the cost of the whole nuclear warhead programme at pounds 410m. Mr Peden says this fails to take into account the means of delivering the weapon - Trident subs and all the other ships, planes and submarines needed to defend them, as well as the submarine bases and personnel.
The defence review says its estimates include "the cost of decommissioning weapons withdrawn from service". But it does not appear to include the cost of decommissioning the nuclear submarines designed to fire missiles.
Last December, Lord Gilbert, Minister of State at the Ministry of Defence, told the House of Lords: "The cost of providing, operating, maintaining and disposing of the Royal Navy's ballistic missile submarine fleet and its missiles is estimated to be some pounds 530m in the current financial year."
This is on top of the Government's figure of pounds 410m, making pounds 940m spent on all aspects of having a nuclear deterrent. CND claims that even this figure is an underestimate and might be as high as pounds 1.5bn.
The organisation argues that only proportions of the cost of bases like Faslane and Coulport are included in the Government's figures when without Trident they would have no purpose.
CND spokeswoman Louise Edge said: "We want the Government to come clean and give a line by line detailed account - one that reveals the total cost of Britain possessing and operating nuclear weapons and does not attempt to fox the public with clever accountancy techniques or sophistry."
The Ministry of Defence said the figures published in its review were the most transparent ever. A spokesman said CND was deliberately "misrepresenting" their meaning. He said that the higher figure quoted by Lord Gilbert included some residual costs from the decommissioning of Polaris, Trident's predecessor. These were not included, however, because the review was intended to be "forward-looking" and Polaris does not figure as part of Britain's deterrent.Reuse content