Shadow Defence Secretary Emily Thornberry has slammed the Tories for their "silence" on the cost of renewing Trident - and on disarmament plans.
Amid speculation that David Cameron will hold a Commons vote on upgrading the nuclear weapons system this summer, Thornberry claimed that the Government had no plan to meet the UK's non-proliferation obligations.
In a speech to the RUSI think tank, she also sought to reframe the Labour debate over Trident by claiming that nuclear disarmament had been at the heart of the party's approach ever since Clement Attlee.
The Shadow Defence Secretary is currently heading up a review of Labour's policy on the nuclear deterrent and is expected to deliver her interim report by the end of this month.
Activists hope that the review will plot a 'third way' between scrapping Trident, protecting defence jobs and a taking a 'step down the nuclear ladder'.
In her speech, Thornberry said that the "rapidly escalating" cost of commissioning a new generation of Trident submarines currently stood at £41bn.
And "on the costs of the warhead, maintenance, and associated infrastructure, there is only silence" from the Ministry of Defence, she said.
But she said that there was "another issue on which there is an equally disturbing silence" - disarmament more generally.
"In the past when major decisions have been made on the future of Britain’s nuclear capability, they have gone hand-in-hand with strong commitments to eventual multilateral nuclear disarmament," she said.
Labour’s original decision to renew Trident in 2007 was accompanied by a statement from then Foreign Secretary, Margaret Beckett that "my commitment to the vision of a world free of nuclear weapons is undimmed."
Despite pressure from Jeremy Corbyn and party members, the Thornberry review may not result in a change in party policy if it is blocked by trade unions at the party conference this year.
The conference is set to feature the most heated debate on nuclear policy since the 1957 conference in Brighton, when Nye Bevan made his famous speech warning that unilateral disarmament would mean sending a British Foreign Secretary 'naked into the conference chamber'.
But Thornberry said Bevan, then Shadow Foreign Secretary, was also a passionate believer in multi-lateral disarmament.
"One line from that speech is best-remembered, but it is worth recalling what preceded it.
"Bevan said: 'It is not a question of who is in favour of the bomb, but a question of what is the most effective way of getting the damn thing destroyed. It is the most difficult of all problems facing mankind.'
"That was the basis of his plea that no British foreign secretary should be sent naked into the conference chamber to negotiate disarmament."
The Shadow Defence Secretary said that the Cameron government had failed to deliver on the Nuclear Non-Proliferation Treaty (NPT), signed by Harold Wilson in 1968.
"Six decades on, what would Bevan make of the fact that the bombs are still with us, now in more countries than ever, but that the conference chamber he talked about lies silent and empty?
"And while there are many other equally difficult problems also now facing mankind, like climate change, terrorism, global poverty, and the state of the world economy, huge attention is being paid to each of those, while almost none is being paid to the issue of disarmament."
She said that the NPT was "effectively a bargain between the countries that had nuclear weapons, and pledged to disarm, and the countries that didn’t have weapons, and promised not to develop them".
"Under this Tory government, that duty has been deserted. That is why we hear the growing frustration of the majority of the world’s countries with the inertia on nuclear disarmament from countries like our own."
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