Tory leader David Cameron and Labour Prime Minister Gordon Brown came together in last night's TV Leaders' Debate in an effort to defend the widely questioned and expensive replacement of Trident nuclear submarines.
Leading military figures, including a former Head of the British Army have questioned the strategic value, cost and priority of the weapon system, which will cost between £10-20 billion to replace (there is disagreement about the figures, and the nature of the project).
Churches and peace campaigners have described the weapons as immoral, redundant and wasteful.
Of the political parties in the election, the Greens, SNP and Plaid Cymru are categorically opposed to Trident, and deny that Britain's much-vaunted "independent nuclear deterrent" fits the bill at all - with the key actually being tied in with the US.
The Liberal Democrats say that they will put Trident into a post-election strategic defence review, but indicate that their existing position is that the "Cold War system" (a term also used by strategic and military analysts) is not adaptable to the current changed and changing security environment. They do not believe a like-for-like replacement is necessary or viable.
A Royal United Services Institute (RUSI) poll of the military, defence and security 'community' this week shows a majority still conservatively behind Trident, but also illustrates an overwhelming desire for a major shift in strategic priorities which many say would leave it irrelevant to the major concerns.
In the Sky TV Leaders' Debate, also available on radio and supplementary TV through the BBC, Lib Dem leader Nick Clegg raised the Trident issue in response to a question about Afghanistan - to which he pointed out it was not relevant - and held to his view that going ahead with the nuclear system regardless would be irresponsible.
This is a view shared by many in the Labour Party, which is nevertheless locked at the top and in government by an Atlanticist and pro-nuclear consensus, at a time in which the US president Barack Obama is seeking to break the nuclear deadlock.
Mr Brown tried to accuse Mr Clegg of "anti-Americanism", a charge he strongly rejected.
In the key exchange, both David Cameron and Gordon Brown defended Trident and sought to pressure Nick Clegg, but were accused in turn of failing to address the issues of the future.
Mr Cameron appeared slightly sheepish in having to say "I agree with Gordon", and Mr Clegg responded robustly to Mr Brown's rehearsed "get real, Nick" jibe by saying that committing to an expensive and out-of-date weapons system with no review in a changing word was not realistic.
Critics point out that the Lib Dems are still supportive of the highly questionable "independent deterrent" argument, and that there is an unbroken consensus on this among the three big parties.