The government is due to reveal its preferred option in December.

"People should bear in mind over the next few months on this issue that if North Korea has nuclear weapons, if there are other states threatening to have nuclear weapons, then it doesn't make sense to take unilateral action," Brown said.

"What we need is multilateral action," he told the Scottish Labour Party's conference in Oban on mainland Scotland's west coast.

"We have taken multilateral action since 1997. We've reduced the number of warheads, we've reduced the firepower of these warheads.

"We've taken action in the international community to promote multilateral disarmament and we will continue to do so."

Lawmakers will be allowed to vote on whether the government should replace Trident.

But members of the governing Labour Party will be expected to follow the party line -- despite more than 120 Labour lawmakers having lobbied ministers to give them a free vote, raising the prospect of another rebellion against Blair.

Trident has proved to be divisive issue between left-wing "old" and centre-left "new" Labour lawmakers under the pro-nuclear Blair, who became party leader in 1994 and prime minister in 1997.

Britain's current nuclear deterrent was set up in the 1980s when the Soviet Union -- not global terrorist groups such as Al-Qaeda -- was seen as the primary threat.

It is based on four 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.

They each have 16 multiple warhead nuclear missiles with a range of 12,000 kilometres (7,500 miles).

If ministers do decide to replace Trident, they would have to choose whether to stick with a purely submarine-based deterrent or utilise land- or air-based systems.

Replacing the deterrent is likely to cost anywhere from 10 billion to 25 billion pounds (19 billion to 48 billion dollars, 15 billion to 37 billion euros), observers say.

earlier related report
British lawmakers to vote on replacing nuclear deterrent
London (AFP) Nov 23 - British lawmakers will be allowed to vote on whether the government should replace its Trident nuclear deterrent missiles, Prime Minister Tony Blair's official spokesman said Thursday.

Ministers will bring forward proposals on a successor to Trident before the end of the year, which will be followed by a "period of debate", the spokesman told reporters.

But the vote, expected early next year, will be "whipped" and not free, said Jack Straw, who as Leader of the House of Commons is in charge of managing government business in the lower chamber.

Whipping is a system where lawmakers are coerced to not only attend a vote on a major issue but to back the party line.

A free vote makes it easier for them to follow their consciences.

The decision to whip the vote is likely to prove controversial with more than 120 Labour lawmakers having lobbied ministers to let them have a say on the issue, and raises the prospect of a backbench rebellion against Blair.

Trident has proved to be divisive issue for the ruling Labour Party under the pro-nuclear, modernising Blair, who became leader in 1994.

Opposition to nuclear weapons and power was historically a central plank of Labour Party policy and disagreement over the current position underlines differences between left-wing "old" and centre-left "new" Labour.

In the 1980s, party leaders such as Neil Kinnock spoke at marches organised by the Campaign for Nuclear Disarmament (CND).

Blair has indicated he wants to keep the nuclear deterrent, as has his probable successor, finance minister Gordon Brown.

But senior ministers including Foreign Secretary Margaret Beckett reportedly have concerns about Trident.

The main opposition Conservative Party believes in keeping Trident, while the second opposition party, the Liberal Democrats, wants to retain a minimum deterrent "for the foreseeable future".

Britain's aging nuclear deterrent consists of four Royal Navy submarines, one of which is always on patrol, fitted with US-built Trident missiles.

It will become obsolete in the mid-2020s. A successor would require many years of development and could cost up to 25 billion pounds (37 billion euros, 46 billion dollars), observers say.

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