The former deputy PM admits that Labour has taken a "kicking"
John Prescott has told Labour dissenters to get behind Prime Minister Gordon Brown or "pay a heavy price".
Promoting his autobiography at the Hay Festival in Powys, the Welsh-born former deputy prime minster said Labour was going through a "difficult" period.
But although Labour had had "a good kicking", the party would pull through.
The Hull East MP also warned that proportional representation such as that used in the Welsh assembly would hit Labour support in its "heartland".
He told the festival that Mr Brown remained the "best man" to deal with the economic problems facing the UK.
Mr Prescott was deputy to Mr Brown's predecessor Tony Blair from Labour's first landslide victory in 1997 until last year.
His comments were part of a discussion about his newly published autobiography - in which he calls Mr Brown "frustrating, annoying, bewildering and prickly" when he was chancellor of the exchequer.
The description came at a time when polls showed that only one in five of the public thought the PM was doing a good job.
Mr Prescott's portrayal has been criticised as "unhelpful" by some Labour MPs.
But, at Hay Mr Brown could not have booked a better mascot.
"People have written off the Labour Party time and time again over the last 18 years," said Mr Prescott.
"That is not to say we haven't got a difficult situation - we have. People have given us a good kicking."
But while some issues were reflected at the ballot box, with a very poor performance in local elections and defeat in the Crewe and Nantwich by-election, Labour's former deputy leader said the government could not take the blame for the current high fuel and food prices.
But he said the party would be judged on how it handled those issues.
When asked to elaborate on the "tension" between Mr Blair and Mr Brown, Mr Prescott stressed that the current PM was the "wronged man" as his predecessor had repeatedly reneged on promises to resign as leader.
His book, Prezza: Pulling no Punches, is an honest, thoroughly readable and frank account of his life story.
He does not shy away from unhappy times such as when his affair with Tracy Temple was revealed, admitting: "I made a mistake, I didn't whine, I was responsible for what happened."
The important thing for him, he said, was to maintain respect and yet, he knew that "he'd let people down - his family, the party" as a consequence of the affair.
His battle with bulimia was also discussed: "People are so ignorant about the illness and so I wanted to inform and help others who are bulimic to speak-out too," he said.
What became clear when listening to the former deputy leader and when reading his book is that he saw himself as an "Old Labour" missionary within New Labour.
In response to such a claim, he was asked whether he should return to his place of birth, Wales - as Welsh Labour had nourished its traditional roots, according to one audience member.
"I have always been in favour of regional and devolved assemblies" he said.
Yet he is less keen on proportional representation (PR), which is used to elect some Welsh assembly members.
Using the platform to warn First Minister Rhodri Morgan and Welsh Labour, he said, "I am concerned about PR - it will reduce the level of support for Labour in this heartland, Wales"
On a UK level, Mr Prescott claimed that he "maintained the balance between old principles and the New Labour direction.
"I never used the phrase New Labour but I recognized that it was necessary under Tony Blair," he said.
In the mid 1990s Labour needed to gain support if it was to win, and so the party had to change
"Tony reflected that change," added Mr Prescott.
But he warned: "Voters will only come back if they think you've changed."