Since the demise of the Soviet Union, does Britain still need a nuclear deterrent?
The PM has refuse to commit to a vote on replacing Trident
That is the question posed by the House of Commons defence committee which is calling for a public debate on the future of Trident.
It also concluded that in our post-9/11 world, nuclear weapons are useless in the fight against terrorism.
So why do politicians, including Chancellor Gordon Brown, want to keep them?
The committee's conclusion was welcomed by the Campaign for Nuclear Disarmament.
But defence experts suggest any future threat could be of a far more complex nature than that from the Soviet Union which gave rise to the deployment of the Trident system.
Dr Paul Cornish, head of the international security programme at international analysts Chatham House, does not believe nuclear weapons could justifiably be used against a terrorist group.
However, he still thinks holding on to them would still have a deterrent value.
"It would seem to be part of a terrorist operational plan to expect to be harried and attacked by conventional forces using conventional weapons.
"If it is made clear that there is and could be no form of attack beyond the conventional then what's to stop a terrorist 'going nuclear' if they can expect just more of the same treatment?"
The MoD is yet to offer a formal response to the defence committee.
MPs said if its officials believed the value of the nuclear deterrent was as an insurance policy, rather than in response to any specific threat, they should justify such an opinion.
The insurance policy argument is a view subscribed to by Lee Willett, of military think-tank, the Royal United Services Institute, who gave evidence to the committee.
"Our future remains entirely unpredictable and it is impossible to predict what threats to the UK may emerge in the next 50 years," he said.
"A nuclear deterrent is an insurance policy and, while a direct nuclear threat to the UK may seem incredible today, what would be the costs to the UK of thinking it no longer needs a deterrent only to be proved wrong?"
Opponents have argued that it is hard to see the UK ever using a nuclear weapon independent from the US.
And the Campaign for Nuclear Disarmament is among those to contend that under the Nuclear Non-Proliferation Treaty, Britain should not replace Trident but move towards total nuclear disarmament.
"If we embark on replacement, we are effectively starting a new nuclear arms race that will send the worst possible message to other countries in the world, some who do not yet have capacity," said Kate Hudson, CND's chairwoman.
Ms Hudson remains worried about the possible timetable for any public debate given that the prime minister has already told MPs a decision on replacing Trident would be taken later this year.
Downing Street has promised a parliamentary White Paper on whether to replace Trident but has refused to commit to a vote in the Commons.
Meanwhile, Dr Cornish from Chatham House said he does not believe there will be "real" debate on Trident replacement "if by 'real' we mean a fully-informed, genuine choice between having a nuclear deterrent and not having one".
"The world is becoming less, not more safe as far as nuclear weapon proliferation is concerned," he added.
"This lends weight to the 'insurance policy' idea.
"And given the stakes involved, most politicians and decision-makers would probably find not having the nuclear option to be an unacceptable risk."