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 on Wednesday.
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.
"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 will say according to advance extracts.
"Because the truth is this. We're in a global race today, and that means an hour of reckoning for countries like ours. Sink or swim, do or decline."
Mr Cameron will also push for a recovery in the world's seventh biggest economy built on "hard work, strong families, taking responsibility and serving others."
His speech appeared aimed at building a sense of national solidarity in the face of plunging poll ratings for the Conservatives, who are in a turbulent coalition government with the smaller Liberal Democrats.
The coalition came to power in 2010 vowing to cut a record deficit, but harsh austerity measures have failed to prevent a double-dip recession and many Conservatives fear for their seats in the next elections due in 2015.
His conference address will echo the tough message of his finance minister George Osborne, who on Monday said the government will slash Britain's welfare bill by a further £10 billion by 2016-17.
The speech has been billed as a make-or-break moment for his leadership as his own popularity ratings are also plunging and he faces a possible challenge from London Mayor Boris Johnson.
His unusually confessional tone comes after the leader of the main opposition Labour party, Ed Miliband, won praise with a highly personal speech that sought to usurp the Tories' traditional slogan as the "one nation" party.
Mr Cameron will draw on his experiences with his disabled late father and his wheelchair-bound son Ivan, who died in 2009, to urge Britons to give something back to society.
"There is nothing complicated about me," he was set to say. "I believe in working hard, caring for my family and serving my country. And there is nothing complicated about what we need today."
Mr Cameron will say that Britain -- a nuclear-armed NATO member whose monarch Queen Elizabeth II is head of the Commonwealth of mainly former British colonies -- is being "tested".
"This is still the greatest country on Earth. We showed that again this summer. Twenty-second in world population, third in the medals table" in the London Olympics, Mr Cameron was set to say.
"But it's tough, these are difficult times, we're being tested. How will we come through it? Again, it's not complicated. Hard work. Strong families. Taking responsibility. Serving others."
Labour shadow cabinet office minister Michael Dugher responded by accusing the government of being unable "to deliver the big response".
"Rather than uniting Britain, his (Cameron's) priority is to cut taxes for 8,000 millionaires by £40,000 next April, while asking pensioners to pay more."
The Conservative leader is seeking to play down the image of what left-leaning British newspapers dub the "nasty party", saying that they had to show they could be "compassionate."
In a move that will dismay right-wingers in his party opposed to his support for gay marriage, Mr Cameron will say the "Conservative party is for everyone: North or South, black or white, straight or gay."
The right of the party is also urging him to take a stand against the European Union and Mr Cameron on Tuesday hinted at holding a referendum on the issue.