The former Labour leader, Mr Neil Kinnock, yesterday made a vitriolic attack on the London mayoral hopeful, Mr Ken Livingstone, accusing him of destroying the Greater London Council and of inventing the "loony left".
Mr Kinnock's comments came after a second opinion poll suggesting Mr Livingstone, the MP for Brent East, was far ahead of his rivals for the job.
A Mail on Sunday survey found 42 per cent of Londoners backed Mr Livingstone, with 25 per cent supporting the Tory candidate, Lord Archer, 13 per cent choosing the former Labour minister, Ms Glenda Jackson, and just 12 per cent favouring the former health secretary, Mr Frank Dobson.
But Mr Kinnock, now vice-president of the European Commission, told BBC1's On the Record that Mr Livingstone's poll ratings were the result of his long headstart in declaring himself a candidate.
"For 18 months Ken has been running . . . He's had 18 months to advertise himself and I think these very early polls that we've seen show the effect of that."
Mr Kinnock, who fought bitter battles with the party's left wing during the 1980s, added: "When people get down to remembering Ken's real record as the man who brought about the destruction of the GLC, the man who invented the London loony left and everything that went with it, then they'll say, `We really don't want this guy to represent [what is] I think the greatest city in the world'.
"We want somebody who will do the job seriously and do it in the cause of London rather than to provide himself with a permanent platform for opposition."
Mr Kinnock said he would be backing Mr Dobson, seen as the favourite of the Labour leadership.
The Foreign Secretary, Mr Robin Cook, also backed Mr Dobson yesterday.
The Mail on Sunday poll suggested Mr Livingstone's chances of success would actually increase to 48 per cent if he was banned by Labour from running as the party's official candidate and stood as an independent. Mr Dobson could only count on 22 per cent of votes as the official Labour candidate.
The poll of more than 1,000 Londoners suggested that any attempts by Mr Blair to "fix" the voting system, in an attempt to scupper the chances of the former Greater London Council leader, could backfire.
Seventy-seven per cent of those polled said the Prime Minister should not try to stop Mr Livingstone from becoming the official Labour Party candidate.
Labour has announced its candidate will be chosen by an electoral college, in which party members in the capital receive just one-third of the votes, with MPs and MEPs having another third and unions making up the difference.
The system was initially seen as likely to block Mr Livingstone, but a number of unions have announced they are to ballot their members, in one case with a recommendation in favour of Mr Livingstone.