LONDON: The other day anti-nuclear campaigners begin their traditional Easter march from Trafalgar Square to the quaintly named Atomic Weapons Establishment in Aldermaston, Berkshire.

Up to now, governments - Labour and Tory alike - have brushed it aside as a benign ritual, to be patronized or scorned. The point of the march cannot be dismissed so easily for much longer.

The traditional notion of nuclear deterrence is being challenged as never before as Washington embraces the doctrine of pre- emptive strikes. That is why such conservative adherents of deterrence theory as Henry Kissinger and Sir Michael Quinlan, former top nuclear apologist at the Ministry of Defence, were so opposed to the invasion of Iraq. (Deterrence wasn't given a chance.)

The Bush administration is coming under growing pressure from elements in the defence establishment to develop "mini-nukes". In a little-noticed report recently obtained by the Federation of American Scientists, the Pentagon's advisory Defence Science Board said the US should invest in low-yield nukes. These, it says, would be much more credible, since they would create less radioactive fallout than existing weapons.

"The United States is moving away from the high-yield city- obliterators of the cold war and seeks to develop smaller, tactical, nuclear weapons, such as deep penetrating bunker busters or mini-nukes, which are regarded as more flexible and usable," says Rebecca Johnson, director of the Acronym Institute for Disarmament Diplomacy.

At Aldermaston, a 2bn-plus pounds sterling investment programme is under way on a project that would enable Britain to produce a new generation of nuclear weapons. A spokesman for the plant told the Guardian, when it was first disclosed two years ago, that the huge expansion plan would provide scientists with the capability to design and produce "mini-nukes" or nuclear warheads for cruise missiles.

Paul Rogers of Bradford University echoes the point. "The usability idea is increasing markedly, the deterrence idea is decreasing markedly," he says. "We are on a slippery slope.

In the run-up to the Iraq invasion, Geoff Hoon, the defence secretary, said: "I am absolutely confident, in the right conditions, we would be willing to use our nuclear weapons." He insisted that the government "reserved the right" to use nuclear weapons if Britain or its troops were threatened by chemical or biological weapons. We were being told for the first time that a UK government would be prepared to launch a nuclear first-strike against a non-nuclear state.

The government's official line on why we need nukes was spelt out in the MoD's defence white paper published in December. It says that the "continuing risk from the proliferation of nuclear weapons, and the certainty that a number of other countries will retain substantial nuclear arsenals, mean that our minimum nuclear deterrent capability, currently represented by Trident, is likely to remain a necessary element of our security".

After repeating the claim that nuclear weapons are the "ultimate guarantor of the UK's national security", it adds: "Decisions on whether to replace Trident are not needed (in) this parliament but are likely to be required in the next one.

We will therefore continue to take appropriate steps to ensure that the range of options for maintaining a nuclear deterrent capability is kept open until that decision point."

If the decision has to be taken in the next parliament, then in its next manifesto Labour will have to say what it intends to do with our nuclear weapons and why. The white paper referred to options for "maintaining" such weapons, not abandoning them.

Yet what's the point of keeping them now that the notion of deterrence has been abandoned? That has been confirmed by those in Washington and London who advocate pre-emptive strikes against potential enemies. But they admit "rogue states" and terrorist groups would not be deterred by the threat of nuclear attack, however small or "clean" the weapon.

In which case, what is the point of Britain clinging on to an ageing nuclear ballistic missile system, which is entirely dependent on the US? Military commanders with their feet on the ground say there is little point, since whatever credibility might have been given to deterrence theory in the cold war, it is no longer valid - as ministers themselves appear to admit. Thus the only point in having them is to use them.

Despite Hoon's comments, that a Blair government would actually fire a Trident missile with a nuclear warhead does seem incredible. The only point in keeping the system, military sources say, is political - ministers want to be on the "top table" and, anyway, the French won't give up their nukes. -Dawn/The Guardian News Service.