Ed Miliband made a forceful appeal for the centre ground on Tuesday, when he adopted the Tory 'One Nation' tradition as his own.
Addressing the Labour Party conference in Manchester, the Labour leader said the country needed to be united if it was to survive the current economic crisis.
"Every time Britain has faced its gravest challenge, we have only come through the storm because we were one nation," he said.
"We wont the war because we we were one nation, we built the peace because we were one nation. To come through the storm, to overcome the challenges we face, we must rediscover that spirit, that sprit the British people never forgot, that spirit of one nation."
Miliband and his wife Justine arrive at Manchester Central ahead of his keynote speech
The term 'One Nation' is attributed to the 19th Century Tory prime minister Benjamin Disraeli who promoted a belief in the need for the state to help improve the lives of working men and the paternalistic need for the rich to look after the poor.
But Miliband said David Cameron had abandoned that tradition in favour of giving tax cuts for the rich and dividing the country.
Speaking without notes from the conference stage, Miliband said: "Let us remember what Disraeli was celebrated for, it was a vision of Britain where patriotism, loyalty, dedication to the common cause, which courses through the veins of all and no one feels left out.
"I do believe in that spirit, that spirit of one nation. One nation where every one has a stake, one nation where everyone's prosperity is fairly shared, one nation where we have a shared destiny."
By stealing the traditional Conservative slogan, Miliband was also delivering a message to the far left-wing of his own party in an attempt to shake-off the potentially damaging "Red Ed" label.
"We can't go back to Old Labour," he told the hall. "We must be the party of the private sector just as much as the party of the public sector."
"We must be the party of South just as much as the party of the North. We must be the party as much of the squeezed middle as much as those in poverty.
He added: "There is no future for this party as the party of one sectional interest of the country."
While David Cameron has in the past claimed to be heir to the One Nation tradition, Labour has been pushing the message that the prime minister has lurched to the right since coming to power.
In a direct and angry attack on Cameron which brought loud applause from Labour members, Miliband said the prime minister had not only prioritised "tax cuts for millionaires", but was incompetent.
To rapturous applause he savaged the coalition: "Have you ever seen a more incompetent, hopeless, out-of-touch, U-turning, pledge-breaking, make-it-up-as-you-go-along, back-of-the-envelope, miserable shower than this Prime Minister and this Government?"
"You can't be a One Nation prime minister if you raise taxes on ordinary families and cut taxes for millionaires. You can be a One Nation prime minister if all you seek to do is divide the country."
Hitting Cameron with his own party's recent slogan, he said: "This prime minister said 'we're all in it together'. Don't let him tell us again 'we're all in this together'."
He added: "They're not going to build one nation, so it's up to us. One nation, a country for all, with everyone playing their part, a Britain we rebuild together."
Miliband's trick of adopting the One Nation mantle is not new, Tony Blair attempted to claim it as his own while in opposition in the mid-1990s.
In a snap response to the speech, Cameron's spokesperson said: "Totally substance free. Claimed One Nation while fighting a class war".
While the Liberal Democrats claimed Miliband had stolen Nick Clegg's Spring 2012 conference speech in which he said: "A one nation party seeing not what divides us – but what unites us".
A Lib Dem spokesperson said: "In his speech to Labour Party Conference he 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."