Mr Meacher says the current Labour leadership is undemocratic

The ex-environment minister told BBC Two's Daily Politics a candidate from the "centre left" of the party should challenge Chancellor Gordon Brown.

Mr Meacher attacked Mr Brown for "bouncing" the party into a commitment to renewing Britain's nuclear weapons.

Asked if he would run against Mr Brown, he said "we will give our attention to that" when the time was right.

Poor showings in two by-elections on Thursday have led to fresh calls for Mr Blair to name a date.

But party chairman and Blair loyalist Hazel Blears said critics would not get "this fabled, mythical timetable" for the prime minister's departure.

'Proper debate'

The left of the party has meanwhile been angered by Mr Brown - the man widely expected to take over - signalling he would replace Britain's Trident nuclear weapons system.

Mr Meacher, who has been touted for several months as a candidate from the left, said there had to be " proper debate" about Trident and even a referendum on the issue.

"We need to concentrate the public's minds around the arguments," he told the Daily Politics.

"The international situation has completely changed with the end of the cold war" and "the biggest issue across the world is terrorism and for those purposes they are completely useless".

Asked if this meant he would run against Mr Brown, he said: "As I have said in the last two years, when Tony Blair does step down I think there should be a contest - nothing to do with Gordon Brown.

"And when there is a contest there should be a candidate for the centre left, there may be from the Blairite right, as well.

"But when that time comes, there is no vacancy, no election, then we will give our attention to that."

Nothing off-limits

This weekend sees Labour's National Policy Forum - a conference designed to give ordinary Labour members an input into party policy.

A Labour spokesman said the policy-making process had produced three election-winning manifestos.

He insisted no issues were off limits at the event and Labour ministers would be debating everything from citizenship, prosperity and "Britain's place in the world" with party members and members of the public.

But Mr Meacher told the BBC News website that on issues such as Trident and nuclear power the party leadership was "totally undemocratic".

He pointed to a YouGov poll last month which suggested the vast majority of Labour members did not feel they had enough influence over policy.

Neal Lawson, of centre left pressure group Compass, who was accused earlier this year of attempting to oust Mr Blair, accused the Labour leadership of ignoring its members.

"If they want people to trust them as political leaders

He said Mr Blair's attitude towards the Labour party was formed when it was "full of wild-eyed Trotskyites".

But he added: "If he is not careful there won't be any people left in the Labour Party at all."