EDINBURGH (Reuters:

British Prime Minister Tony Blair's pledge to quit within a year failed to heal rifts yesterday as his likely successor came under fire from a respected Labour Party heavyweight.

Former Interior Minister Charles Clarke launched a stinging attack on finance minister Gordon Brown, the man most expected to succeed Blair after a decade of at times tense and testy relations with his leader.

Brown addressed party supporters in Edinburgh about the importance of national unity yesterday, but steered clear of any reference to the leadership or Clarke's comments and breezed past waiting media after the speech.

After a junior minister and seven government aides resigned to protest against his continued leadership this week, Blair sought to quell the rising rebellion by promising to be gone within a year. But he refused to give a precise date.

Blair's popularity has tumbled in opinion polls as government scandals over sleaze and mismanagement have been compounded by controversy over the wars in Iraq and Lebanon.

Brown and then Blair sought on Thursday to put an end to a week of fevered speculation that had threatened to paralyse the government and left the ruling party looking divided.

But Clarke, who also recently accused Blair of poor leadership, put paid to any hopes of peace breaking out.

In an interview with yesterday's Evening Standard newspaper, Clarke accused Brown of "absolutely stupid" behaviour in the crisis that engulfed the government.

He issued a stark warning that Brown must now "prove his fitness" to succeed Blair and said of his Labour colleagues in parliament: "A lot of them are worried about Gordon and need to be reassured."

"SHUT UP NOW"

Blair's official spokesman declined any comment on Clarke's remarks and one cabinet minister called for an urgent end to bickering about the leadership.

"I really do think it's quite a serious situation," said Minister for Justice Harriet Harman. "I really think everybody should shut up now."

But members of parliament and party activists continued to stoke the fire under Blair's leadership.

Labour lawmaker John Smith said Blair's position was now untenable: "He'll have to go sooner rather than later."

Ken Munro, a Labour Party member for 50 years who attended Brown's speech, said the mood in the party was poisonous.

"Charles Clarke's comments were not unconsidered. They were done with malice and aforethought. He should be ashamed."

Trade union chiefs, who help to bankroll the Labour Party, also warned that the party risked losing the next election, expected in 2009, unless Blair stood down immediately to give a new leader time to revive support and reshape policy.

"Unless something changes, Labour will lose the next election," said Derek Simpson, head of Britain's second biggest union, the Labour-affiliated Amicus.

And the momentum behind Blair's gradual demise showed no sign of easing with banner headlines such as "Blair clings to the wreckage" in the Daily Telegraph.