David Cameron is to warn that Britain faces a stark choice in turbulent economic times - "Sink or swim. Do or decline."

Countries such as the UK are confronting an "hour of reckoning" in the global race for economic recovery, and those which fail to take the right decisions may not return to the prosperity they enjoyed before the financial crash, the Prime Minister will say.

The grim message comes in a speech to the Conservative Party conference in Birmingham which aides characterised as a "serious and frank analysis of the challenges facing the country" which will affirm the PM's determination to stick to his Plan A of deficit reduction.

Labour's alternative Plan B, of borrowing more in the hope of boosting growth, would "hurt the economy and hit people hard" by forcing up interest rates, he will warn.

In a highly personal speech, Mr Cameron will explain how his family history helped form his political beliefs, which he will sum up as "Hard work. Strong families. Taking responsibility. Serving others."

He will reveal how his father, Ian Cameron, helped support his own mother when she was deserted by her husband. His father's commitment to providing for his family despite his disability meant his life was "not a hard luck story, but a hard work story", he will say.

Mr Cameron's speech draws down the curtain on a conference in which he has been accused of taking his party to the right, with £10 billion of welfare cuts, new protections for householders who attack burglars and the prospect of a referendum on Europe. But he will insist that he has not abandoned the compassionate conservatism he espoused when he won the Tory leadership in 2005, telling delegates that Conservative policies are "not just good for the strong and the successful but the best way to help the poor and the weak and the vulnerable".

He will deride Labour leader Ed Miliband's bid to snatch Disraeli's One Nation mantle in his own conference speech last week, making clear that he is not ready to cede the Tories' claim to the political centre ground.

But the key theme running through his speech will be the economic peril facing the UK and the need to stick to the path of austerity which the coalition Government has set out upon. "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," Mr Cameron will say. "Because the truth is this - we are in a global race today and that means an hour of reckoning for countries like ours. Sink or swim. Do or decline."

Labour's shadow Cabinet Office minister Michael Dugher said: "Britain does face big challenges - from the double-dip recession to one million young people out of work - but the Government can't deliver the big response. David Cameron can't be the One Nation Prime Minister we need to lead the way in tackling them. Rather than uniting Britain, his priority is to cut taxes for 8,000 millionaires by £40,000 next April, while asking pensioners to pay more."