David Cameron will tomorrow promise a revolution in the way that central government operates if he becomes Prime Minister, so that the state delivers "more for less" in Britain's "age of austerity".
Addressing his party's spring conference in Cheltenham, the Tory leader will call for a "change of culture" so that the public sector takes its share of the burden, in order to bring down the record borrowing figures revealed in this week's Budget.
But Mr Cameron will defy Labour demands for him to spell out in detail where his public spending cuts would fall. Ministers will increase the pressure on him to "come clean" this weekend, warning that cuts to front-line services would be inevitable under a Tory Government.
"The times are too serious for David Cameron's marketing speak," Liam Byrne, the Cabinet Office minister, said last night. "He must stop playing fantasy politics and hide and seek with the voters. We have set out our plans in the Budget. Now it is time for him to set out his."
But the Tory leadership will argue that the doubts already expressed about Alistair Darling's Budget forecasts – which could raise borrowing in the current year beyond the £175bn he predicted – shows that it would be wrong to spell out the party's economic prospectus in full until they have studied the books after the election. "The uncertainties are so great that we have no idea what they will look like," one Tory source said.
Tory officials said the Opposition would not walk into a "Labour trap" by promising to reverse the 50p top rate of income tax that will bite on earnings above £150,000 a year from next April.
Yesterday, Mr Cameron said the move was "a mistake" and "bad for Britain" as he tried to reassure Tory traditionalists who want him to pledge to scrap the rate.
But he stopped short of doing so in a round of media interviews. He said: "We don't approve of the high marginal tax rates which will do damage to Britain. But it's got to form its place in the queue of taxes we want to get rid of. How do we get rid of them? By getting to grips with spending now."
Today, William Hague, Mr Cameron's unofficial deputy, will address the new generation of Tory parliamentary candidates in Cheltenham. The party has now chosen candidates in more than 300 constituencies.
In a separate speech to the main conference, the shadow Foreign Secretary will accuse Gordon Brown of heading "the most financially disastrous, blindingly incompetent, grossly dishonest and disgustingly grubbiest of all the governments in the modern history of our country".
He will claim that the Prime Minister is acting in a "narrow, partisan and factional" way rather than as the leader of a great country.
"We need to tackle Labour's debt crisis by making sure government lives within its means, and that the Conservative answer is fiscal responsibility with a social conscience," Mr Hague will say. "For nothing is more damaging to a nation's future, more corrosive of its prospects and more draining of its energies, than to load on to the shoulders of future generations the burden of paying for the economic mismanagement of today. It is above all today's children who will end up cursing the day that their parents and grandparents elected Gordon Brown."
He will add: "The Conservatives will once again have to clean up this rotting mess; we will once again pick up where a government that has run out of everyone else's money has left off, and rebuild the prosperity and position of our country."
Mr Hague will appeal to Mr Brown to restore trust in politics by calling the referendum that Labour promised on a new EU treaty.
"Our Prime Minister was not elected to his office by anyone. He ran away from an election and then ran from a referendum," he will say.