The Government was today facing renewed pressure to re-think its decision to update its Trident nuclear deterrent in the face of growing cost pressures on the defence budget.
A report by a high-level commission for the Institute for Public Policy Research (IPPR) think-tank urges ministers to consider whether the submarine-based system is the most cost-effective way of maintaining Britain's "minimum" deterrent capability.
The recommendation is one of a raft of proposals, covering the whole spectrum of Britain's national security, made by the commission chaired by former defence secretary Lord Robertson of Port Ellen and former Liberal Democrat leader Lord Ashdown of Norton-sub-Hamdon.
Other members include former chief of the defence staff Lord Guthrie of Craigiebank, former UK ambassador to the United Nations Sir Jeremy Greenstock, and former Association of Chief Police Officers president Sir Chris Fox.
In its report, the commission called for major innovations in defence policy to adapt to the "post 9/11 and post recession world", with investment in cyber-warfare, command and control, and the creation of a joint civilian-military stabilisation and reconstruction taskforce.
It said that there should also be strengthening of the special forces in order to deal with a Mumbai-style terror attack in the UK.
At the same time it called for a review of £24 billion of existing defence equipment projects with a view to making cuts, with the new aircraft carriers, the joint strike fighter, the Type 45 destroyers and the Astute class submarines all "in the frame".
On Trident, the commission said that while it believes that Britain does still need a minimum UK deterrent, this should be reviewed as part of a wider strategic review of UK security going beyond just defence.
It suggested that one option could be a further life-extension for the ageing Vanguard class submarines which carry the Trident missiles beyond the current five-year run-on to 2024 already planned.
It said that Britain should be be prepared to put part or all of its nuclear weapons capability on the table as part of international nuclear disarmament negotiations.
More broadly, the commission called for a major overhaul of the Whitehall policy-making machinery, with the introduction of a single, cross-departmental, security budget, and a new national security council.
It urged the development of a greater European role in Nato defence, with the UK taking the lead in creating "permanent structured defence co-operation" among a "pioneer group" of EU countries - although not in the form of a European army.
"UK reliance on the United States is complacent and it is delusional to believe the UK can go it alone. We need a major increase in European defence and security cooperation to strengthen Nato," it said.
In other measures, the commission called for a major increase in strategic gas storage capacity to lessen Britain's exposure to "energy blackmail".
It said that Britain should also end the deportation of terrorist suspects on the basis of controversial memorandum of understandings that they will not not face torture and abuse unless they can be backed up by robust, independent monitoring.
Lord Robertson said that in the current strategic climate, greater European co-operation was essential.
"In the post 9/11, post financial crisis world, we must be smarter and more ruthless in targeting national resources at the real security risks and be more willing to make difficult national choices," he said.
"But we also can't delude ourselves. When it comes to security national self-reliance is a dangerous fantasy. European co-operation is the only viable way forward in many areas. We need to make it work."
Lord Ashdown said that in terms of security, Britain needed to change the way it thought and the way it organised itself.
"In a world where power is no longer the sole preserve of nation states, and where security is no longer only about defence, we need new joined-up machinery in Whitehall, a truly integrated strategy that links all of our policy instruments together, and a much greater focus on how we link the UK effort to the efforts of others around the world," he said.
The Defence Minister Bill Rammell said on the BBC Radio 4 Today programme: "We have got the best funding environment for the military since the 1980s, but we do face immense challenges.
"We have withdrawn from Iraq, but we face challenges in Afghanistan and elsewhere, and therefore we constantly keep our policies under review and I welcome this contribution."
Mr Rammell stressed that today's report did not advocate the unilateral scrapping of Britain's nuclear deterrent, and said it was wrong to suggest that alternatives to the submarine-based Trident system may be more affordable.
He said: "We don't put forward proposals to invest in equipment unless we believe it is necessary. We remain committed to the policy we set out two years ago (on Trident).
"We keep it under constant review and that is not very much different at all to what this report is saying.
"Our position is that we remain committed to working towards a world free of nuclear weapons. We are the most forward-leaning nuclear state in terms of disarmament - we have reduced the explosive capability of our nuclear arsenal by 75% over the last 10 years.
"But when we look at the risks moving forward over the coming decades, we don't believe at the moment it would be safe to fail to make decisions now which would effectively commit us to unilateral disarmament in the future, regardless of the circumstances.
"We are talking about our national security. Yes, I believe we can afford it, but we constantly need to keep our position under review and we need to work for multilateral nuclear disarmament, which is what we are emphatically committed to."