Labour must reclaim the political centre ground if the party is to recover from its crushing general election defeat, Tony Blair has warned.
The former prime minister, who led the party to three consecutive election victories, said the party had to show that it stood for "ambition and aspiration" as well as compassion and care.
His analysis was echoed by two of the potential contenders to succeed Ed Miliband as leader from the Blairite wing of the party - shadow business secretary Chuka Umunna and shadow health minister Liz Kendall - who both said the party had failed to speak to "aspirational middle-class" voters.
Meanwhile Mr Blair's former deputy, John Prescott, unleashed a blistering attack on the Labour campaign, pouring scorn on Mr Miliband's "Hell yes, I'm tough" claim and accusing him of failing to defend the previous Labour government's record on the economy.
In contrast, Mr Blair, writing in The Observer, praised Mr Miliband - who dramatically announced his resignation within hours of accepting defeat - for his "courage under savage attack," and the way he put "his heart and soul into the fight".
However he made clear that a change of direction was needed if the party was to stand a chance of regaining power at the next general election.
"The route to the summit lies through the centre ground. Labour has to be for ambition and aspiration as well as compassion and care," he wrote.
"'Hard-working families' don't just want us to celebrate their hard work; they want to know that by hard work and effort they can do well, rise up, achieve. They want to be better off and they need to know we don't just tolerate that; we support it."
Mr Umunna said that while the party's policies were pro-business too often their rhetoric gave the opposite impression while sometimes they appeared to suggest they saw "taxing people as a good in itself, rather than a means to an end".
"We spoke to our core voters but not to aspirational, middle-class ones. We talked about the bottom and top of society, about the minimum wage and zero-hour contracts, about mansions and non-doms. But we had too little to say to the majority of people in the middle," he wrote in an article for The Observer.
"We allowed the impression to arise that we were not on the side of those who are doing well. We talked a lot - quite rightly - about the need to address 'irresponsible' capitalism, for more political will to tackle inequality, poverty and injustice ... But we talked too little about those creating wealth and doing the right thing."
In an interview with The Sunday Times, Ms Kendall confirmed that she was considering a run for the leadership and warned the party was in need of fundamental reform.
"Fundamental reform is essential to the future survival of our party," she said.
"We need to show people that we understand their aspirations and ambitions for the future and if you look right across England, we did not do enough to appeal to Conservative supporters, and we must.
"I think we lost because people didn't trust us on the economy. People didn't think we understood their lives, shared their values and aspirations. For people who aren't on the minimum wage or on zero hours contracts, or (who) own their own homes, we were saying far too little."
Writing in the Sunday Mirror, Lord Prescott said it had been a "bloody disastrous" result for the party.
"We fought a presidential-type election based on computers, charts, focus groups and even the American language - Hell yes? Hell no!" he wrote in the Sunday Mirror.
However he said the real roots of their defeat lay in the failure by Mr Miliband and shadow chancellor Ed Balls to confront effectively Conservative claims that the previous Labour government had "wrecked" the economy.
"The Tories and Lib Dems worked tirelessly to sow the seeds of a myth which grew into a publicly accepted 'fact'. As President Clinton said, 'It's the economy stupid'. And we were stupid not to defend it!
"I said to both Eds, both personally and in the Parliamentary Labour Party, that it was vital we nailed these Tory lies. But I was told 'We want to focus on the future, John, not the past'.
"I warned them if we didn't defend the past we wouldn't have a future. This general election has depressingly proved that."