Labour MPs in Sussex are preparing to join a mass revolt over the Government's plan to renew Britain's nuclear weapons system.

At least three of the county's five Labour MPs have vowed to defy the party line in the Commons tonight and vote against proposals to replace Trident.

The rebels - David Lepper (Brighton Pavilion), Des Turner (Brighton Kemptown) and Michael Foster (Hastings and Rye) - are expected to back an amendment which calls for the decision on the £20 billion plans to be delayed.

The county's two other Labour MPs, Laura Moffatt (Crawley) and Celia Barlow (Hove and Portslade) told The Argus they had not yet decided how they would vote.

It means none of Sussex's five Labour MPs has pledged to back the Government's motion supporting a new generation of nuclear submarines capable of firing Trident D5 missiles.

With more than 60 Labour MPs threatening to rebel, Prime Minister Tony Blair faces the humiliation of having to rely on Tory MPs to carry it through.

The Tories have said they will vote for a Trident replacement and the Lib Dems - including Lewes MP Norman Baker - have vowed to vote against the plans.

In a sign of the Government's desperation to get its backbenchers to toe the party line, Ms Barlow, who said she had "a lot of concerns" about renewing Trident, has been given one-on-one audiences with Foreign Secretary Margaret Beckett and Defence Secretary Des Turner in an attempt to bring her round.

The Labour rebels said voting now to renew Trident would be wrong because: o The new deterrent would not be independent - it would be reliant on the United States.

o It would be "hypocritical" to threaten Iran and North Korea over their nuclear ambitions while renewing our own capacity.

o The cost of replacing and maintaining a successor to Trident, which the Campaign for Nuclear Disarmament says could reach £76 billion, would be better spent on equipment and kit for troops.

o The key threat to the UK is terrorism from individuals, not state aggression.

Brighton Pavilion MP David Lepper, who first joined CND in 1961 and has met survivors of the Hiroshima bomb, said: "I have always felt morally, strategically and financially it was a mistake for us to have nuclear weapons. I certainly see no good reason for taking the decision now to renew Trident."

Hastings MP Michael Foster, whose only previous rebellion was against the decision to invade Iraq in 2003, said: "We need to show North Korea and Iran we are moving downscale in terms of nuclear proliferation. Upgrading our capacity would send the wrong message."

Brighton Kemptown MP Des Turner said: "The case for renewing Trident gets weaker by the year. This is a protest vote but it's an important protest to make."

Eileen Daffren, chairwoman of Sussex Peace Alliance, part of the Campaign for Nuclear Disarmament network, praised the "courage and vision" of the rebels and urged Ms Moffatt and Ms Barlow to join the revolt.

"They should all be voting against," she said. "People who didn't see the effects of Hiroshima don't understand what a nuclear bomb would do."