Chris Huhne: There are better things to do than replace Trident

Is this relic of the Cold War justified and is the cost an efficient use of military resources?

Voltaire famously stated that the Holy Roman Empire was neither holy, nor Roman, nor an Empire. I suspect that Trident as presently constituted is neither British, nor independent, nor a deterrent. The £15-20bn estimated for its replacement with a similar system is not the best use of defence funds.

There are more pressing military priorities for our troops in Afghanistan and Iraq: body armour, helicopters, armoured personnel carriers and medical care. In this leadership contest, Liberal Democrats need to take a hard look at our party's position.

British nuclear weapons have had a political dimension from the outset. Churchill built a hydrogen bomb so that we could resume our wartime nuclear partnership with the US. Nuclear weapons allowed Macmillan to abolish conscription.

In 1957, Macmillan even persuaded President Eisenhower to resume the US-UK wartime special relationship on nuclear matters. The following year, after we successfully exploded a hydrogen bomb, Congress passed the UK-US agreement on the "Uses of Atomic Energy for Mutual Defense Purposes" (note the spelling even in the Parliamentary version). This allowed the US to send us its nuclear weapon designs. Since 1958 all so-called British weapons bar one have been based on US designs. Macmillan in 1962 then persuaded President Kennedy to sell us the Polaris missile system. Since that time our nuclear delivery systems have been totally American. The Trident missiles in our submarines are not even owned by Britain. They are taken from a pool kept in King's Bay Georgia. We are entitled to no more than 58 missiles in total at any one time. So the Trident missile is not British.

There was however a condition attached to Polaris. Macmillan noted in his diaries: "I have agreed to make our present bomber force (or part of it) and our Polaris force (when it comes) a NATO force for general purposes. But I have reserved absolutely the right of H.M.G. to use it independently for 'supreme national interest."

Tony Blair renewed this pledge regarding Trident in a letter to President Bush last year. The Trident fleet, normally, is assigned to NATO. Since the end of the cold war NATO no longer has been unable to agree a nuclear policy so "assigned to NATO" means integrated with US nuclear forces. Thus the Trident fleet is not independent.

Nor is it clear that the UK's nuclear weapons deter any state from anything. It did not deter Argentina from invading the Falklands. Nor did it deter Iran from seizing the British naval personnel.

It is therefore time for a fresh look at why we continue to possess nuclear weapons; is this relic of the cold war justified today, and is the cost an efficient use of military resources? As an economist, I know that there are opportunity costs associated with any decision: if £20bn is spent on a Trident replacement, it cannot be used to equip our troops.

Finally, I am and have always been a friend of the US. But to be a friend does not imply a lack of candour or that US interests should come before our own. Harold Wilson refused to send our troops to Vietnam despite Lyndon Johnson's urgent requests. The tragedy of Tony Blair is that he aligned UK policy with US policy on Iraq, without thinking through its consequences.

The next 50 years will be wholly unlike the past 50 years. The US has its own interests. Already, it has very different approaches to global warming, the International Criminal Court, international law, the death penalty and the treatment of prisoners. Yet the government decision to replace Trident assumes that US-UK relations will remain closely aligned over the next 50 years.

US-UK relations should remain close, but the UK should cease to act as if it were a US satellite. In the case of Trident, that precludes continuing the present arrangements when a final decision on replacement needs to be made in a few years time, soon after the 2010 non-proliferation treaty review. In the light of the overall political, economic and military situation at that time, we should then assess whether to deploy a new system or go for other options.

A smaller deterrent than Trident, if we needed one,might well be more vulnerable, but might nevertheless retain the essential principle of deterrence – the risk of unacceptable consequences for an aggressor – against any likely threat from rogue states if not terrorists. But the loss of prestige if we fail to support our peace-making and peace-keeping forces with adequate equipment could be far greater. It is surely time to make tough choices on a Trident-style system.

The writer is a Liberal Democrat leadership contender.