LONDON (Reuters) - Prime Minister Tony Blair could face one of the biggest rebellions by the Labour Party in a decade in power on Wednesday when parliament votes whether to renew Britain's nuclear arsenal.
As many as 100 Labour MPs could reject Blair's plan to spend up to 20 billion pounds on three or four nuclear-armed submarines to replace the ageing Trident system.
That would be the biggest rebellion against Blair since nearly 140 Labour politicians voted in 2003 against war in Iraq and Blair's biggest setback on a domestic issue since he came to power in 1997.
Blair, who has a majority of 67 in the 646-seat Commons, is expected to win with the help of the Conservatives who have said they will back the replacement.
Blair, due to step down in a few months, argues Britain must retain nuclear weapons because new threats from Iran, North Korea or nuclear terrorists make it dangerous to abandon them.
Opponents say there is no need for the weapons now the Cold War is over and Britain will set a bad example to countries such as Iran and North Korea by insisting on keeping them.
"Our decision could well be the hinge point between real impetus towards stopping proliferation or a trigger leading to a cascade of further proliferation...," Michael Meacher, a left-wing Labour legislator who will challenge for the party leadership when Blair goes, said in a statement.
Critics say the money could be better spent and complain they are being rushed into a decision by an outgoing prime minister eager to create a legacy.
Nigel Griffiths, deputy leader of the Commons and a member of the government, resigned on Monday in protest at Trident's replacement. Jim Devine, a ministerial aide, was also reported to have quit on Tuesday although he could not be reached for confirmation.
The government argues design and construction of new submarines will take so long that it must act quickly to have a replacement ready when the existing nuclear submarines go out of service in about 2024.
"You have to make a decision now because of the long lead times involved ... If you don't do so then you are de facto making a decision not to replace Trident," Blair's spokesman said on Tuesday.
The government said in announcing its proposals in December it would cut Britain's nuclear warheads by 20 percent to fewer than 160 and may reduce its submarine fleet to three from four.
A deep hostility to nuclear weapons runs through the Labour Party, which espoused unilateral nuclear disarmament until the late 1980s. Almost two-thirds of Labour MPs who took part in a poll released on Sunday opposed the plan.