Alan Johnson gave David Miliband a clear run for the Labour leadership after he ruled himself out of any future contest and hinted that the Foreign Secretary was his choice to succeed Gordon Brown.

“David’s got a great future in the party,” the Health Secretary said in an interview with The Times. He said that he was not interested in being Labour leader. “I haven’t got any false modesty but I don’t aspire to that job.”

Although Mr Johnson said that he had never been a Brown cheerleader, he thought that the Prime Minister was the best person to lead the country “at the moment” because of his role in tackling the financial crisis. He made plain that he was against a leadership contest now, believing that Mr Brown should be given time. He said critics should “shut up” because they were damaging the party.

He admitted, however, that the Cabinet was not in a happy mood and he criticised Mr Brown’s handling of last year’s election speculation and the abolition of the 10p tax rate.

Mr Johnson was seen as one of Mr Miliband’s main rivals and his endorsement of Mr Miliband will be viewed as a crucial development as the Labour conference begins in Manchester today. Next week Mr Brown will tell voters that he is the best man to lead by highlighting his role in helping the country to withstand the fallout from the Wall Street crash.

If he fails to restore his authority, Mr Miliband will be the favourite to succeed him. Mr Johnson is out of the race and it is believed that James Purnell, the Work and Pensions Secretary, will be unlikely to stand in any contest against Mr Miliband.

Speculation that Mr Miliband was mounting a leadership bid rose after he wrote an article in July rallying Labour, but without mentioning Mr Brown. In a interview with The Times published today in the Magazine, he defended the piece. Mr Johnson praised Mr Miliband’s article as a “well-reasoned, brilliant exposition of where the party needs to be and about getting our confidence up . . . No one was entitled to disparage David Miliband. He is a huge talent in the party. Anyone looking at David Miliband sees a very, very good, competent politician who is part of our solution to these problems, not part of the problems themselves. David has got the common touch . . . given his intellectual power and his background, he is very down to earth and very modest. I hope he goes a long way because I’m a big fan of his.”

In his own interview, Mr Miliband was careful not to step out of line, suggesting that “of course” Mr Brown would lead Labour into the next election. He said that his article “went bigger than I expected”. He said that he was inspired to write it because Labour members “wanted the leadership showing a sense of fight”.

Clearly trying to dismantle his geekish, brainy image, he said that “a big heart matters more than a big brain”. He also confirmed that he did not believe in God.

Last night Mr Miliband urged Labour rebels to “pull together” behind Mr Brown and not be defeatist. On his way to the conference, he told the Daily Mirror: “I’ve made it clear I don’t think it’s the time for a leadership election. It’s time to address the fundamental challenges — that’s why it’s the time to pull together.”

Mr Brown is determined to ensure that leadership speculation does not drag him down. Yesterday he hinted that his critics were not as tough as he was. He told Sky News: “I spent the summer doing what I think I should be doing: looking at what we had to do with the housing market, looking at what we had to do on the gas and electricity market. These are difficult times. Some people may think that, because of difficult times, they’re not able to be as tough as I am on getting through them. That is their business.”

In a YouGov poll for The Daily Telegraph, 68 per cent of respondents said Mr Brown had blown his chance as Prime Minister. Tory support stood at 44 per cent, Labour was on 24 per cent and the Lib Dems were on 20 per cent.

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