Ed Miliband has delivered a highly-personal speech in which he insisted Labour is now the "One Nation" party.
The Labour leader borrowed the One Nation slogan first used by Tory prime minister Benjamin Disraeli in the 19th century and long linked to the political centre-right.
He insisted David Cameron had lost his right to call himself a One Nation Prime Minister by cutting the top rate of tax and slashing services and benefits for the poor.
Britain can overcome the current challenges by coming together as it had in the past, he said, adding: "One nation: a country where everyone has a stake. One nation: a country where prosperity is fairly shared.
"One nation where we have a shared destiny, a sense of shared endeavour and a common life that we lead together. That is my vision of one nation, that is my vision of Britain, that is the Britain we must become."
The keynote address to the party conference in Manchester was deliberately very personal as Mr Miliband sought to recast himself as a man of the people.
It followed a new ComRes poll for the Independent which showed that just 22% of people believe he has what it takes to be a good Prime Minister.
Lasting more than an hour, it was delivered from memory with no notes at all in a move that will inevitably spark comparisons to key speeches made by Mr Cameron in 2005 and 2007.
Aides said Mr Miliband had written the speech himself in the past few weeks and decided to deliver it off the cuff in a bid to connect more with the audience.
It was light on policy announcements apart from widely trailed education reforms and was immediately criticised for only briefly mentioning the economy.
Mr Miliband did vow to split up the banks, repeal the controversial NHS reform Bill and establish an alternative to the A-level for the "forgotten 50%" who do not go to university.
But the focus was on his own philosophy, which he explained had been forged through his experiences as the child of Jewish refugees from Nazism and days at a London comprehensive school.
Mr Miliband said his political views were moulded after family friend Ruth First, a campaigner against apartheid in South Africa, was killed in a letter bomb attack.
He spoke of how his Jewish mother was rescued during the war by nuns and his father joined the Royal Navy after fleeing the Nazis.
"It is this upbringing who has made me a part of who I am - a person of faith, not of religious faith but a faith nonetheless. A faith I believe many people will recognise," he said.
"Here is my faith. I believe we have a duty to leave the world a better place than we found it. I believe we cannot shrug our shoulders at injustice and just say that is the way the world is, and I believe we can overcome any odds if we come together as people."
Attempting to contrast his life with the Home Counties upbringing of the Prime Minister, he says: "My conviction is rooted in my family's story, a story that starts 1,000 miles from here, because the Milibands haven't sat under the same oak tree for the last 500 years.
"My parents came to Britain as immigrants, Jewish refugees from the Nazis. I would not be standing here today without the compassion and tolerance of our great country, Great Britain, a country that my parents saw rebuilt after the Second World War."
Of his schooling at Haverstock School in North London, he adds: "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."
There were only glancing references to internal party critics and the Liberal Democrats, with his fire mainly focused on the Tories and their record in office.
He argued that nothing had changed since 2010 and that the economy is now getting worse rather than better.
His accusation that the Tories had shown themselves to be "incompetent" despite believing "they were born to rule" brought the audience to its feet.
"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?" he asked.
Attacking the move to slash the top rate of tax, he vowed that his government would govern for the public and private sectors, for the squeezed middle and for the poor.
And he sought to draw a distinction with past Labour leaders by insisting it would not be silent about irresponsibility at the top and would hold the most powerful in society to account.
Mr Miliband warned of further austerity to come as he insisted the country had to learn to live within its means, but he stressed that those with the "broadest shoulders" should suffer most.
He said: "Every time Britain has faced its gravest challenge we have only come through the storm because we were one nation."
Immediately after the address, general secretary of Unite Len McCluskey said it was a "tour de force" that showed the Labour leader is a prime minister in waiting.
Former labour leader Lord Kinnock added: "It was brilliant in all respects."