Ed Miliband has attempted to snatch the centre ground of British politics by declaring that Labour is now the "one-nation" party.
The phrase - normally associated with moderate Tories - was repeatedly used by the Labour leader as he roamed the conference stage at Manchester.
He spoke for more than an hour, without notes, in a highly personal speech that contained few new policies.
He vowed to unite the nation and lead it through tough economic times.
BBC Political Editor Nick Robinson described the speech as an "audacious" attempt to "steal a traditional Tory slogan" and "fill the space he believes has been vacated by David Cameron in the centre ground of British politics".
He said it was greeted by Labour activists in the hall with what seemed to be a sense of relief that they had chosen a leader who might yet take them to Downing Street.
During his 65-minute address to the packed hall, Mr Miliband invoked the spirit of the Olympics and World War Two as examples of what Britain can do when everyone pulls together, while criticising the Conservatives and Liberal Democrats.
'Change the medicine'
He got a standing ovation when he called Prime Minister David Cameron and the coalition government a "U-turning shower".
But he also went out of his way to court disillusioned Tory voters, telling them he understood why they had voted for Mr Cameron in 2010.
He said Mr Cameron had let them down and he mounted a sustained attack on the coalition government's efforts to stimulate an economic recovery.
He said: "When David Cameron says to you 'Let's just carry on as we are and wait for something to turn up', don't believe him, don't believe him. If the medicine isn't working, change the medicine.
"And I tell you what else to change - change the doctor too, and that is what this country needs to do."
Mr Miliband said the country could not carry on as if it were, "as two nations, not one, the bankers and the rest of the country".
"We must have a one-nation banking system as part of a one-nation economy."
The Labour leader cited as his inspiration a former Conservative Prime Minister, Benjamin Disraeli, who made a famous speech on One Nation Conservatism in Manchester's Free Trade Hall, now a luxury hotel opposite Labour's conference venue.
He said Labour would not be able to reverse all of the coalition's spending cuts if it won the next election but promised a fairer approach to cuts and policies to promote growth.
The speech contained few new policy announcements but Mr Miliband did unveil proposals for a new qualification - the technical baccalaureate - to be taken at 18.
This would transform the lives of the "forgotten" 50% of young people in England who do not go to university, the Labour leader said.
Mr Miliband, who praised the work of the police and armed forces, also talked about growing up as the son of Jewish refugees who fled the Nazis.
"My family hasn't sat under the same oak tree for the last 500 years," he said.
"I was born at my local NHS hospital, the same hospital where my two sons were born. And I went to my local school with people from all backgrounds.
"My school taught us a lot more than just how to pass exams: it taught people how to get on with each other, whoever they are and wherever they were from."
Mr Miliband declared that the next Labour government would reform education and apprenticeships - in partnership with business - to create a more highly skilled and highly paid workforce.
The new certificate would replace the dozens of existing vocational qualifications with a single "gold standard" exam, which would also include maths and English.
Labour would also reform apprenticeships, giving control of the £1bn budget for on-the-job training to business and allowing firms more of a say in setting the standards for vocational qualifications, he said.
'Labour isn't learning'
Mr Miliband also stressed that being a one-nation party meant fighting to preserve the United Kingdom in the forthcoming Scottish independence referendum - prompting scathing response from the Scottish National Party.
"The extraordinary message in Ed Miliband's speech is that Labour now amounts to nothing more than a party of one nation Toryism," said SNP MP Angus Robertson.
A Lib Dem spokesman said Mr Miliband had "attempted to airbrush out his and Labour's record in power".
"On taxes, youth unemployment and taking on vested interests, Liberal Democrats in the coalition government are delivering where Labour failed," he added.
Conservative Party Chairman Grant Shapps also accused Mr Miliband of failing to learn "from the mistakes that Labour made in office".
"Instead he failed to back our welfare cap, failed to back our immigration cap and still stands for more spending, more borrowing and more debt - exactly what got us into this mess in the first place. Sadly, Labour isn't learning."