Labour chairman Hazel Blears has launched her bid for the party's deputy leadership, saying Labour must remain the party of success and aspiration.
Ms Blears wants the party to re-establish its "big tent" coalition
She also warned that it would be a mistake for the party to distance itself from Prime Minister Tony Blair.
Ms Blears is the sixth MP to enter the race to replace John Prescott when he stands down with Mr Blair this year.
She called for the renewal of the "big tent" coalition which brought Labour victories in 1997, 2001 and 2005.
Some other challengers - including ministers Peter Hain and Harriet Harman - have been seen to be trying to reconnect with Labour's core voters, by criticising huge City bonuses and the wealth gap.
But it was by being the party of success and aspiration that Labour had won the last three elections, Ms Blears said.
Speaking in her Salford constituency as she launched her bid, Ms Blears said: "We have to stay in tune with people's ambitions."
She added: "We must use this leadership election and the transition to a new leadership team to showcase our party, its values and its policies to new supporters and voters."
Ms Blears, seen as a Blairite, has dismissed suggestions that she should stand down as party chairman to fight the contest.
A source told the BBC last week that she had received a "strong" show of support from MPs and party members.
Her entry into the race means there are now six declared runners for the deputy's job, with Cabinet ministers Hilary Benn and Alan Johnson and backbencher Jon Cruddas also in the race, in addition to Ms Harman and Mr Hain.
Ms Blears, 50, who was promoted to the Cabinet last May, has consistently defended Blairite policies ranging from tuition fees to the Iraq war.
But she recently sought to demonstrate her independence by campaigning against maternity ward closures in her Salford constituency, at a time when the government is under pressure over the NHS.
Her decision to join a demonstration against the closure of a maternity unit in her constituency prompted her political rivals to accuse her of "double standards", for campaigning against government policy.
She launched her campaign in a regeneration area which aides have described as a "metaphor for Labour government". Public Health Minister Caroline Flint will be her campaign manager.
Chancellor Gordon Brown is still seen as the firm favourite to replace Mr Blair, but on Wednesday, veteran left winger Michael Meacher said he wanted to challenge him for the party leadership.
He said Labour members deserved a say in the party's future direction and insisted it was not a "foregone conclusion" that Mr Brown would be the next prime minister.