Harriet Harman, the Justice minister, has been elected to the Deputy leadership of the Labour party.
Gordon Brown was also declared as Leader of the Labour party at a special conference in Manchester.
Tony Blair remains Prime Minister until Wednesday. He will give a farewell performance at Prime Minister’s Questions before going to see the Queen and resign.
Gordon Brown will then be asked by the Queen to form a government.
Details of Mr Brown’s first Cabinet will be revealed throughout Thursday.
The party used an electoral college to elect the Deputy Leader, split three ways between the MPs and MEPs, the party membership and members of affiliated unions and socialist societies.
As no candidate got 50% or more of the vote outright, further elimination ballots were held.
The polls closed on Friday. Around 99% of Labour MPs and MEPs, 56% of constituency party members and only 9% of union members voted.
Ms Harman had argued that a woman should replace John Prescott. In an interview with PinkNews.co.uk, she warned younger gay voters against the charms of David Cameron.
“I just want to say to those people that can’t remember what it was like under the Tory party, they absolutely represent that dark part of politics which is quite comfortable with discrimination, with prejudice, and so it’s like a warning.
“This is a dangerous moment,” she said.
Ms Harman’s victory was a surprise result – Education Secretary Alan Johnson was tipped to win.
On gay rights, Ms Harman told PinkNews.co.uk:
“The fact is the Tories are now agreeing with us, but we have got to remember that it was Labour who fought against Section 28, fought for civil partnerships and fought for a right not to be discriminated against on grounds of sexual orientation.
“What we did is said ‘we are in government, we want to be in government to do these things.’
“The Tories argued against to begin with. We had taken a strong lead, we have changed the weather, and the Tories come on our ground.
“Without Labour being in government we would have still been in the climate that the Tories left us with ten years ago.”
It is not thought that Ms Harman will be appointed Deputy Prime Minister.