Gordon Brown's failure to give taxpayers value for money will be the "terrible legacy" of this government, says Conservative Oliver Letwin.
Labour is turning its golden rule to dross, says Mr Letwin
The shadow chancellor said Mr Brown's credibility was falling because there were deep failures in public services despite him taxing and borrowing more.
He pointed to experts' claims of a £10bn black hole in public finances.
The exchanges over Thursday's pre-Budget report set the economic battle lines for the next general election.
Mr Letwin ridiculed ministers' efforts to cut waste and bureaucracy.
This year, 4,000 civil service posts had been advertised in one newspaper alone, he said.
And the number of tax collectors had risen more than twice as much as the number of nurses.
Mr Brown might be searching for a holy grail but was more "Sir Waste-a-lot" than Sir Lancelot, he joked.
"Our public services are not working," he said. "After 66 stealth tax rises, why are there one million people on hospital waiting lists?
"After taxes have gone up £5,000 per family per year in Britain, why are 5,000 people dying of infections picked up in dirty hospital wards in our country?"
Mr Letwin said the chancellor should have heeded the advice of new European Commissioner Peter Mandelson and not "gloated" about British economic fortunes.
The Institute for Fiscal Studies says the Treasury risks breaking its "golden rule" of borrowing only to invest, rather than for day-to-day spending, over the economic cycle.
Mr Letwin accused Mr Brown of sliding over such inconvenient facts.
"It is alchemy in reverse: the golden rule has turned to dross in his hands," he argued.
The Tory spokesman said Thursday's plans would not make up for the despair felt by many pensioners who had suffered a 70% increase in council tax.
Businesses had also suffered from excessive regulation.
"The chancellor's failure to give Britain's taxpayers value for money will be the terrible legacy of this government," he added.
Mr Brown hit back by challenging the Tories to "come clean" about their plans to cut funding for public services.