Harriet Harman, the Justice Minister, has been elected as Deputy Leader of the Labour Party in a surprise victory at a special conference in Manchester today.

Ms Harman pipped Alan Johnson, the Education Secretary, in a head-to-head battle after five rounds of voting by an electoral college.

Gordon Brown, who officially became Labour leader today, announced later that Ms Harman will also be Labour Party Chairman. He will declare on Thursday, the day after he becomes Prime Minister, whether she will also be Deputy Prime Minister.

The other candidates for the deputy race who were eliminated, round by round, were: Hazel Blears, the outgoing Labour Party chairman; Peter Hain, the Northern Ireland Secretary; Hillary Benn, the International Development Secretary; and the left-wing backbench MP Jon Cruddas.

Ms Harman was chosen by an electoral college that was split into thirds between MPs/MEPs; the party membership and the trade unions. She polled 50.43 per cent of the vote in the final round against Mr Johnson’s 49.56 per cent after all the other candidates were eliminated, as none gained an overall majority.

As a percentage of the overall votes from the electoral college Ms Blears was in 6th place and eliminated first, Peter Hain fifth, Hillary Benn fourth, John Cruddas third and Mr Johnson second.

Mr Cruddas - who ran unashamedly as a candidate for the Left - surprised many with the strength of his performance today. It is likely to be regarded as a sign of growing disaffection in certain sections of the party with the new Labour project.

A party spokesman insisted that around 1,000 new members had been recruited every week during the contest. But only half of party activists and less than 10 per cent of eligible trade unionists are believed to have bothered to vote.

Ms Harman said it was an “honour and a privilege” to be elected deputy leader and to work alongside Mr Brown.

She said she was confident about the future because of what Labour had achieved in ten years in Government. She said that the party owed an “enormous debt” to Mr Blair and her predecessor John Prescott and wished them well for the future.

But criticised Mr Blair’s leadership style and said there was “anger and division” over Iraq. “You want our plans to be debated and presented to Parliament, not briefed and spun to the media. “You want us to acknowledge the anger and division caused by Iraq, and we do, but we must give our total support to our armed forces as they support Iraq’s fragile democracy.”

Ms Harman, 55, the MP for Camberwell and Peckham, has had a topsy-turvy career, joining the Cabinet in 1997 as Social Security Secretary, but was sacked in 1998 by Tony Blair along with her deputy Frank Field after the two fell out over welfare reform.

Her bid for the deputy leadership may well have been helped by her Old Labour credentials. She was on the front bench through much of the 1980s and is married to Jack Dromey, the Labour Party treasurer and deputy leader of the Transport and General Workers Union.

Ms Harman’s campaign focused largely on her appeal to women voters and her record in promoting gender equality. She has been described as Labour’s “in-house feminist”.

Ms Harman returned to the Government in 2001 as Solicitor General and now holds the title of Justice Minister after the Department of Constitutional Affairs took on responsibilities from the Home Office and was renamed the Ministry of Justice.

Even before Labour came to power, Ms Harman found herself embroiled in controversy as shadow health secretary when she sent her son to a grant-maintained school.

At today's conference, Mr Brown spelt out his vision for a Labour government which could stay in office until 2010, by which time he has to call a general election.

He told delegates: “It is with humility, pride and a great sense of duty that I accept the privilege and the great responsibility of leading our party and changing our country. “I will endeavour to justify every day and in every act the trust you have placed in me.”

The Chancellor will walk through No 10 Downing Street on Wednesday after Mr Blair has conducted his last Prime Minister’s Question Time in the Commons and handed in his Seals of Office to the Queen at Buckingham Palace.

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