TONY BLAIR is expected to announce plans today to update Britain's Trident nuclear deterrent - as he was warned the issue was potentially "explosive" for the Labour Party.

The Prime Minister will reveal proposals for a new generation of nuclear-powered submarines that carry the Trident missiles, enabling the deterrent to continue to the middle of the century.

Ministers have promised MPs a Commons vote on whether to go ahead early next year.

But with many Labour MPs deeply opposed to a replacement, former Defence Minister Peter Kilfoyle yesterday urged Mr Blair not to rush to a decision.

"Politically, it is extremely sensitive," he told BBC Radio 4's The World This Weekend.

"I think it is a very inopportune moment to be replacing Trident. I think it sends out entirely the wrong message.

"We don't even know the putative enemy that these things will be pointed at in the future.

"It was a weapon that was designed for the Cold War and it is not necessarily appropriate in the future.

"We need a full and protracted debate. We don't need to rush to some kind of decision over the next few months, as appears to be the Government's wish."

Mr Kilfoyle is the latest prominent Labour figure to question the need for a decision now, following interventions from former Home Secretary Charles Clarke and deputy leadership contender John Cruddas.

Ministers have said that a decision is necessary because the submarines start coming to the end of their lives from 2020 and replacements will take 14 years to design and build.

Shadow Defence Minister Julian Lewis said that it was highly probable that the Conservatives would back the Government in the Commons vote.

"We have said all along that our policy is that Britain should retain the existing nuclear deterrent and replace it when necessary," he said.

However, Liberal Democrat defence spokesman Nick Harvey said he believed the Government had several years before it needed to make a final decision.

He said: "I think Tony Blair is pushing this politically because he believed he saved the Labour Party from unilateralism with the whole New Labour project, and he wants one of his last deeds to be shackling them into the nuclear business for another generation."

The former head of the Royal Navy, Admiral Sir Alan West, warned that in an "extremely dangerous, unpredictable and chaotic world" it would be a mistake to give up the deterrent.

He said: "In that very, very dangerous world, I think it would be extremely foolhardy to give it up.

"The messages we would give, I think, by giving it up would be very strange."

He said that the long design and lead-in time meant that the submarines could be scrapped nine years from now if they were no longer considered necessary.

* Labour MPs are divided over whether the Government should replace the nuclear deterrent, according to a poll. A survey for The Independent newspaper finds 50 per cent of Labour members want to retain the deterrent as against 39 per cent who do not.