Four Army generals have written in today's Times , saying Britain should be prepared to scrap the Trident nuclear weapons system.
Rapid cuts in nuclear forces are "the way to achieve international security", they say.
Their comments come before Thursday's Prime Ministerial debate between the leaders of the three main parties, which will focus on foreign policy.
Both the Prime Minister and the Conservative opposition support the renewal of Trident, although the cabinet is reported to be split on the issue. Trident renewal has been strongly criticised by a range of churches, faith groups, NGOs, charities and trades unions.
The Liberal Democrats say they would not replace Trident, but would maintain other nuclear weapons. The Greens, SNP and Plaid have all said the UK should no longer have nuclear weapons.
The Campaign for Nuclear Disarmament (CND) said a few days ago that Trident had become a key election issue .
The latest comments come from Field Marshal Lord Bramall who is a former Chief of the Defence Staff, General Lord Ramsbotham, a former Adjutant-General, General Sir Hugh Beach, a former Master-General of the Ordnance, and Major-General Patrick Cordingley, who is a former Commander of the 7th Armoured Brigade.
They write in today's Times: "It is to be welcomed that all the leading political parties are committed to conducting a comprehensive strategic defence review after the election. This clearly must follow a detailed evaluation of the threats that this country faces today and in the future.
"However, it is of deep concern that the question of the Trident replacement programme is at present excluded from this process. With an estimated lifetime cost of more than £80 billion, replacing Trident will be one of the most expensive weapons programmes this country has seen. Going ahead will clearly have long-term consequences for the military and the defence equipment budget that need to be carefully examined.
"Given the present economic climate, in which the defence budget faces the prospect of worrying cuts, and that we have already an estimated hole in the defence equipment budget of some £35 billion, it is crucial that a review is fully costed and looks critically at all significant planned defence spending.
"The debate has shifted significantly since the 2007 decision to proceed with replacing Trident. Internationally there is a growing consensus that rapid cuts in nuclear forces, starting with the US and Russia, but with the smaller nuclear states following, is the way to achieve international security
"There have been promising developments in the multilateral disarmament process led by President Obama, including the recent US-Russia nuclear arms reduction agreement.
"Through the Nuclear Threat Initiative and Global Zero, a powerful line-up of international statesmen, including Mikhail Gorbachev, Henry Kissinger and Desmond Tutu, have added their voices to the call for a nuclear-free world.
"Such a world would undoubtedly be a safer place, and while it remains a distant and challenging goal, opportunities to bring it closer should be given thorough consideration by any government.
"Serious concerns have also been raised by members of the services and defence analysts about the strategic value of nuclear weapons and their relevance to modern warfare. Indeed, three of us wrote to The Times on this subject in January 2009. These fundamental questions about how and against whom our nuclear weapons act as a deterrent must still be answered.
"The potential impact of a UK commitment to replace Trident on the international disarmament negotiations must also be considered along with its impression on other states. As the former head of the International Atomic Energy Authority Mohamed ElBaradei put it: “It is very hard to preach the virtues of non-smoking when you have a cigarette dangling from your lips and you are about to buy a new pack.”
Any genuinely comprehensive review needs to weigh up all of these issues and answer the question:
“Is the UK’s security best served by going ahead with business as usual; reducing our nuclear arsenal; adjusting our nuclear posture or eliminating our nuclear weapons?
"Should the review determine that there is still a need for a nuclear deterrent, a number of options may be more affordable than a like-for-like replacement of the Trident system, which has been described as a 'Rolls-Royce' solution. The state of the public finances requires each of these options to be carefully evaluated, alongside like-for-like replacement and disarmament.
"It is no longer good enough to skirt round the question of what actual military value an expensive nuclear deterrent provides to our services by labelling the decision a "political one”. This decision will have a direct impact on our overstretched Armed Forces. Allowing the military’s views to be excluded from this decision will have consequences both predictable and regrettable.
"It may well be that money spent on new nuclear weapons will be money that is not available to support our frontline troops, or for crucial counterterrorism work; money not available for buying helicopters, armoured vehicles, frigates or even for paying for more manpower.
"Suppressing discussion of these issues or dismissing alternatives before properly examining them would be a big strategic blunder. All political parties must allow a full and open debate about the Trident replacement as part of the strategic defence review."