Senior government ministers, including Northern Ireland Secretary Peter Hain and International Development Secretary Hilary Benn, backed anti-nuclear campaigners' views that the conference was the last chance for open discussion.

Justice Minister Harriet Harman warned that all British taxpayers would want a say on how their money was spent when Labour leader and Prime Minister Tony Blair makes a decision on a new generation of nuclear weapons later this year.

The chairwoman of the Campaign for Nuclear Disarmament (CND) described the decision as a "travesty of democracy" and accused Labour of contriving to avoid an open debate.

"They seem to be doing anything possible to avoid a debate which is shocking. They are trying to gag debate," she added.

Trident was set up in the 1980s by then prime minister Margaret Thatcher when the Soviet Union -- not global terrorist groups like Al-Qaeda -- was seen as the primary threat.

It is based on four British Royal Navy submarines fitted with US-built Trident missiles which are due to become obsolete in the 2020s. One of the submarines is always on patrol, but the missiles are no longer pre-targeted.

Replacing the deterrent is likely to cost between 10 to 25 billion pounds (15 to 37 billion euros, 19 to 47 billion dollars), observers say, although opponents claim the figure will be higher.

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