No date has been announced for the poll, that depends on when Tony Blair steps down, but with John Prescott recently announcing that he would be standing down as deputy leader, and with MPs returning to Parliament last week, there is now an official vacancy, and scope for serious plotting.

Jon Cruddas, the MP for Dagenham, will steal a march on his rivals tomorrow, opening his campaign at Dagenham and Redbridge football club. His first public parliamentary backers are Jon Trickett, chairman of the Compass group of MPs, and David Crausby, chairman of the Amicus group of trade union MPs.

He already has the support of many senior figures in trade unions and is sending his pamphlet to every elected Labour figure in the country as well as to local parties.

The energy of his campaign has already propelled his odds of winning from 125-1 against, to 8-1, according to the bookmakers William Hill, putting him in third position.

He is opening campaign headquarters at Waterloo and has hired two workers, who are about to head off to Washington for a week to learn tips about internet and community campaigning from Democrats.

Two Cabinet members and a minister have also thrown their hats in the ring: Peter Hain, the Northern Ireland Secretary; Alan Johnson, the Education Secretary; and Harriet Harmen, the Constitutional Affairs minister. Jack Straw, the Leader of the House, and Hilary Benn, the International Development Secretary, are also known to be interested and have been taking soundings.

The four openly declared candidates have formulated their campaign messages and have been presenting them to colleagues. All want to be deputy prime minister if they become deputy leader of the party, apart from Mr Cruddas, who has said he wants to concentrate on running the party.

MPs, Labour Party members and two million members of affiliated trade unions vote for the deputy leader, each block getting a third of the vote.

Candidates require nominations from 44 MPs. Mr Hain, the favourite, has been meeting MPs and is counting on more than 50 for support. His campaign team is run by Dan Norris, MP, his parliamentary private secretary; Paul Goggins, a Northern Ireland minister; and Martin Linton, the parliamentary private secretary for Mr Hain’s rival Ms Harman. Mr Linton said: “I am not in the role of PPS to support the minister in party terms, but in her ministerial job. She has no problem with it.”

Mr Johnson’s team believe that he will have no difficulty recruiting 44 MPs to nominate him. Gerry Sutcliffe, the Home Office minister, who is managing his campaign, said: “I know many colleagues would be happy to support him.”

Ms Harman, who is insisting that the party must have a woman deputy leader, told The Times: “It would be inexcusable to let David Cameron seem more women-friendly than us.”

Although the campaigning has started, no end is in sight, the timetable and rules having yet to be decided.

THE CANDIDATES

Jon Cruddas, MP for Dagenham

Declared supporters Jon Trickett, David Crausby Peter Hain Northern Ireland Secretary

Odds 8-1

Peter Hain, Northern Ireland Secretary

Declared supporters Dan Norris, Paul Goggins, Northern Ireland minister, Martin Linton, David Chaytor

Odds 3-1

Harriet Harman, Constitutional Affairs Minister

Declared supporters Mike Foster, Joan Ruddock, Jim Sheridan, Julie Morgan

Odds 9-1

Alan Johnson, Education Secretary

Declared supporter Gerry Sutcliffe

Odds 4-1

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