David Miliband has warned Labour could be out of power for years as he made his bid for leadership of the party at the final hustings meeting before the vote.
The front runner in the race to replace Gordon Brown shared a platform with brother Ed, along with Andy Burnham, Ed Balls and Diane Abbott, as all five candidates went head to head in a question-and-answer session for 600 party members in Manchester.
David Miliband told the party faithful each time Labour had been thrown out of government they had stayed in opposition for between 14 and 18 years.
"This is a time to be serious," he said.
"We could be out of power for a long time, history tells us we will. I want to buck that trend."
Andy Burnham got the longest round of applause and the biggest cheer as each candidate made a final pitch for votes at the event.
He promised to put the "heart and soul" back into the party and reconnect with, "the ordinary people who have lost faith with Labour".
"We can't have more of the same," he said. "We have to change. We can't have the people's party run by the chattering classes on the London dinner party circuit."
Diane Abbott, described by Ed Balls as the "not candidate" because she had not been in cabinet and could not be blamed for past mistakes, said: "They are all very good aren't they? The young princes, the Top Guns of New Labour."
She said Labour needed to learn from its past, to "change the narrative" and she had called the big issues right such as when she opposed the war in Iraq.