David Cameron targeted "intellectual" Ed Miliband in his keynote speech to the Conservative Party conference on Wednesday afternoon, dismissing the Labour leader's attempt to claim the One Nation centre ground.

Cameron's message was a serious one, warning that the country's very future was at stake and it was he, not Ed Miliband, who was the man to protect it.

"Unless we act, unless we take difficult, painful decisions, unless we show determination and imagination, Britain may not be in the future what it has been in the past," he said.

Introduced by New York mayor Michael Bloomberg and foreign secretary William Hague along with a video montage of him on foreign visits, Cameron sought to position himself as a statesman that only a prime minister can.

"Because the truth is this. We are in a global race today. And that means an hour of reckoning for countries like ours." He added: "Sink or swim. Do or decline."

The best received line in the hall was when he launched a direct attack on Ed Miliband's accusation that the government was writing a cheque to millionaires with a tax cut.

Speaking down to the Labour leader as if he were a child, not a statesman, Cameron said: "Ed... Let me explain to you how it works. When people earn money, it’s their money. Not the government’s money: their money.

"Then, the government takes some of it away in tax. So, if we cut taxes, we’re not giving them money - we’re taking less of it away. OK? Got it?"

Cameron also acknowledged the damage that can be done by the perception that as an Eton educated millionaire himself he is "posh" and out of touch, a view many Tory MPs have admitted could do serious harm to the party at the next election if it sticks.

Cameron said:"I'm not here to defend privilege, I'm here to spread it. I don't have a hard luck story, my dad was a stockbroker from Berkshire."

"To all those people who say: 'he wants children to have the kind of education he had at his posh school', I say: 'yes – you’re absolutely right'. I went to a great school and I want every child to have a great education."

Dismissing Labour Party "intellectuals" - Ed Miliband was a professor - and "Labour theorists", the prime minister said by contrast he was "not complicated".

He said: "I believe in working hard, caring for my family and serving my country. And there is nothing complicated about what we need today."

As widely trailed before his speech, the prime minster used the address to try and wrest back his claim to the centre ground, which Ed Miliband tried to position himself in by adopting the traditional Tory One Nation slogan last week at the Labour conference.

"It’s us, the modern compassionate Conservative party, who are the real champions of fighting poverty in Britain today," he said.

Cameron acknowledged that the party had a "cartoon" reputation as one that did not care. "My mission from the day I became leader was to change that," he said. "To show the Conservative party is for everyone: North or South, black or white, straight or gay."

His voice cracking as he spoke about his son Ivan who died in 2009, Cameron said the Paralympic Games had helped change people's views of the disabled.

"When I used to push my son Ivan around in his wheelchair, I always thought that some people saw the wheelchair, not the boy," he said.

"Today more people would see the boy and not the wheelchair – and that’s because of what happened here this summer."

Labour's Michael Dugher MP, responded to the speech, arguing it showed the prime minster was on the back foot.

"This was a defensive speech, from an out of touch, clearly rattled leader, who cannot be the One Nation Prime Minister we need," he said.

"David Cameron never once mentioned the double dip recession or the one million young people out of work. His speech failed to set out the real change our economy needs.

He added: "Rather than tackling the banks, or explaining why borrowing is going up not down, he chose to defend his millionaires' tax cut."

Loading Slideshow...
  • BRITAIN-POLITICS-CONSERVATIVES

    British Prime Minister David Cameron talks about his late son Ivan during his keynote address on the fourth day of the annual Conservative Party Conference at the ICC in Birmingham, central England on October 10, 2012. Britain faces a sink or swim moment and must take painful action to avoid falling behind its global competitors, Prime Minister David Cameron was set to warn. The struggling Conservative leader will use a crucial speech to his party's annual conference in the industrial city of Birmingham to urge recession-hit Britons to work harder and brace for more austerity. AFP PHOTO / LEON NEAL (Photo credit should read LEON NEAL/AFP/GettyImages)

  • Conservative Party Conference 2012

    Samantha Cameron listens as her husband, Prime Minister David Cameron, as he addresses the Conservative Party conference at International Convention Centre in Birmingham.

  • Conservative Party Conference 2012

    Singer Charlotte Church arrives at the Conservative Party conference in Birmingham to hand a letter to the Prime Minister David Cameron from victims of the press concerned about self regulation.

  • Conservative Party Conference 2012

    Prime Minister David Cameron and his wife Samantha arrive at the Diwan Balti restaurant in Birmingham to celebrate his 46th birthday, whilst in the city for the Conservative Party conference.

  • Conservative Party Conference 2012

    Prime Minister David Cameron arrives for keynote speech with wife Samantha at the Conservative Party conference at International Convention Centre in Birmingham.

  • Conservative Party Conference 2012

    Stage hands prepare the stage for Prime Minister David Cameron keynote speech at the Conservative Party conference at International Convention Centre in Birmingham.

  • Conservative Party Conference 2012

    File photo dated 18/4/2010 of David Cameron greeting his father Ian during a visit to The Sun Inn in Swindon, Wiltshire. Cameron revealed the inspiration he drew from his 'eternal optimist' father Ian in a deeply personal passage in his Tory conference speech today.

  • Conservative Party Conference 2012

    Prime Minister David Cameron and his wife Samantha after his address to today's session of the Conservative Party Conference at Birmingham's International Convention Centre.

  • Conservative Party Conference 2012

    Prime Minister David Cameron and his wife Samantha after his address to today's session of the Conservative Party Conference at Birmingham's International Convention Centre.

  • Conservative Party Conference 2012

    Prime Minister David Cameron and his wife Samantha after his address to today's session of the Conservative Party Conference at Birmingham's International Convention Centre.

  • Conservative Party Conference 2012

    Prime Minister David Cameron with his wife Samantha after his address to today's session of the Conservative Party Conference at Birmingham's International Convention Centre.

  • Conservative Party Conference 2012

    Prime Minister David Cameron and his wife Samantha make their exit after his address to today's session of the Conservative Party Conference at Birmingham's International Convention Centre.

  • Conservative Party Conference 2012

    Prime Minister David Cameron during his keynote speech at the Conservative Party Conference at International Convention Centre in Birmingham.

  • Conservative Party Conference 2012

    Prime Minister David Cameron during his keynote speech at the Conservative Party Conference at International Convention Centre in Birmingham.

  • Conservative Party Conference 2012

    Prime Minister David Cameron and his wife Samantha make their exit after his address to today's session of the Conservative Party Conference at Birmingham's International Convention Centre.

  • Conservative Party Conference 2012

    Prime Minister David Cameron during his keynote speech at the Conservative Party Conference at International Convention Centre in Birmingham.

  • Conservative Party Conference 2012

    Prime Minister David Cameron during his keynote speech at the Conservative Party Conference at International Convention Centre in Birmingham.

  • Conservative Party Conference 2012

    Prime Minister David Cameron during his keynote speech at the Conservative Party Conference at International Convention Centre in Birmingham.

  • Conservative Party Conference 2012

    Samantha Cameron listens as her husband, Prime Minister Prime Minister David Cameron, makes his keynote speech at the Conservative Party Conference at International Convention Centre in Birmingham.

  • Conservative Party Conference 2012

    Prime Minister David Cameron during his keynote speech at the Conservative Party Conference at International Convention Centre in Birmingham.

  • Conservative Party Conference 2012

    Defence Secretary Philip Hammond listens as Prime Minister David Cameron addresses today's session of the Conservative Conference at Birmingham's International Convention Centre.