Harriet Harman, who has borrowed £10,000 to fund her campaign to become Labour’s deputy leader, will learn today whether her expensive overdraft has helped to secure pole position.

Alan Johnson, the Education Secretary, is expected to claim about 60 backers when he announces his bid, lower than the 80 MPs bullish supporters had previously claimed were ready to back him publicly.

Ms Harman named 61 firm nominations yesterday, the largest total so far and a list made more impressive by the inclusion of prominent friends of Gordon Brown, including Ed Miliband, Alistair Darling, Douglas Alexander, Nick Brown and Yvette Cooper.

Her support contrasted sharply with that behind Hazel Blears. Tessa Jowell and John Reid lent their support at a Westminster photo call, confirming the Blairite tinge to the Blears campaign. John Hutton is already backing her.

David Miliband weighed in behind Mr Johnson, backing his claim to be the unity candidate, and joining supporters such as James Purnell and Liam Byrne who are expected to win promotions if Mr Brown becomes Prime Minister. The Johnson camp said many more had pledged to back him but did not wish to declare publicly at this stage, including some ministers and whips, while others wished to talk to their local parties first.

“We know a lot of those will support us. At the end of the day it will be in three figures,” one member of his team said.

Beginning his campaign, Mr Johnson will style himself as a bridge between old and new Labour who can bring the party together. He will say Labour must remain a party of aspiration, offering people a chance to get on and move up in life.

With supporters of Hilary Benn, the bookmakers’ favourite, still admitting he was short of the 45 MPs required to be nominated, the Johnson camp now regards Ms Harman as its main rival. Lord Kinnock, the former Labour leader, endorsed her as the candidate best able to win back voters who have deserted Labour.

The Constitutional Affairs Minister took a £10,000 loan at an interest rate of 14.17 per cent from the National Westminster Bank within days of John Prescott announcing he was quitting last October, The Times has learnt. A spokesman for Ms Harman said: “It’s an overdraft at a commercial rate. It’s what you pay.”

But Lisa Taylor, of Money-facts, a personal finance web-site, said the rate would be “scandalously high” for a personal loan. “Even if this is a business loan I would say it erred on the high side.”

Friends of the wildcard candidate, Jon Cruddas, who has mounted a grassroots campaign calling for a shake-up of party organisation and new policies such as more council houses, claimed that he had the required number of backers.

Peter Hain, the first to announce the 45 names, edged his tally of nominees up to 47. The candidates will spend the cash over the next six weeks as they compete for votes at seven hustings across the country before the winner is announced on June 24.

How they rate

How Gordon Brown rates the contenders for deputy:

Alan Johnson 5/5 Thought to be the favourite. Gerry Sutcliffe, a leading Brownite, is running his campaign. Brown and Johnson have worked closely together

Hilary Benn 4/5 Likely to get high-profile job in Cabinet, possibly Foreign Secretary, but Brown thought to be relaxed either way about him becoming deputy

Harriet Harman 4/5 A longstanding Brownite. Many key Brown allies are backing her, including Yvette Cooper, Douglas Alexander, Alistair Darling, John McFall, Ed Miliband, Geoff Hoon

Jon Cruddas 3/5 Rated by Brown, who thinks he is doing valuable things. Likely to be asked to do a party job. Not as left-wing as many assume; a disillusioned Blairite

Peter Hain 3/5 Very close to Brown, one of the first openly to back him to replace Blair and thought to be keeping a Cabinet post. Further to left of some deputy contenders

Hazel Blears 2/5 Little obvious empathy with Brown. Put herself in the “ultra Blairite” camp in past; backed by some who have difficult relations with Brown, such as John Reid

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