Cabinet minister Hilary Benn has pledged a "more straightforward kind of politics" if he becomes Labour's next deputy leader.
Hilary Benn urged Labour members to have their say
Launching his bid to replace John Prescott, he also said the party should be "unapologetic about our values".
He faces Hazel Blears, Peter Hain, Alan Johnson, Harriet Harman and backbencher Jon Cruddas in the race.
Mr Cruddas' campaign received a boost earlier when London mayor Ken Livingstone backed him.
Mr Livingstone praised Mr Cruddas' "tenacity" in campaigning against the BNP in his Dagenham constituency, in East London, and said he had made a "thoughtful" contribution to the debate on the future of the party.
Mr Benn, who launched his campaign earlier at Toynbee Hall, in East London, was the last of the deputy contenders to gain the required 45 nominations to get on to the ballot paper, Mr Benn's campaign team said he had strong support within the party.
On Friday, the Leeds Central MP told his launch audience, which included his father Tony: "The first task of the deputy leader ... will be to put Labour at the centre of a new and more straightforward kind of politics.
His other aims would be to empower communities and encourage the party to be "bolder" about the society Labour wanted to create.
He emphasised that Labour had to "talk straightforwardly about the future we want" and urged members to vote for the next deputy leader.
"No politician can create this society alone, as real leadership means having the humility to listen as well as the courage to act," he said.
"The corridors of power belong to the British people, and making sure your voice is heard along them is why I am standing to be deputy leader."
The six contenders will take part in a series of hustings around the UK, starting on Sunday in Coventry.
Voting forms will go out to Labour Party members, MEPs and trade unionists from 1 June, with the ballot due to close on Friday, 22 June.
Appealing to Labour's 200,000 members, Mr Benn said it was now time for them to have their say.
"Because this election must not and will not be decided in the corridors of power."
With Chancellor Gordon Brown confirmed as the next prime minister, Mr Benn said the deputy leader should offer "frank advice" to his boss.
Hilary Benn - 47
Hazel Blears - 49
Jon Cruddas - 49
Peter Hain - 51
Harriet Harman - 65
Alan Johnson - 73
Mr Cruddas, the only backbencher on the ballot paper, is to launch his campaign next Tuesday in the West Midlands.
As well as the endorsement from Mr Livingstone, he has the backing Britain's biggest union Unite, which includes Amicus and the Transport and General Workers' Union.
Mr Livingstone said: "Jon Cruddas has impressed me with his thoughtfulness and tenacity and I very much hope that Labour members will back him to become the next Deputy Leader of the Party."
He praised his opposition to nuclear weapons and his stance on fighting child poverty and racism, among other policies.
"Jon Cruddas has shown a strong commitment to the trade unions, which are key to Labour's ability to connect with the concerns of millions of working people," added Mr Livingstone.
"The support that Jon Cruddas has already built up within the trade union movement shows that he will make an effective deputy leader, linking the government with both constituency activists and trade union members."
Unite Joint General Secretary, Derek Simpson, said: "Jon Cruddas' stated policies mirror our members desire for better job security, decent pensions, affordable housing and public services provided by the public sector.
"Jon is unlike any other candidate standing for the Deputy Leadership - he alone is calling for a change of direction in order to reconnect with the Labour Party's core supporters."