The Tories have fired the opening shots of what will be a sustained attack on Gordon Brown's record as Chancellor in an effort to undermine his reputation for economic competence.
George Osborne, the shadow Chancellor, claimed the Mr Brown had failed to prepare Britain for "rainy days ahead" during his decade in charge of the Treasury.
Mr Osborne's attack provoked retaliation from Labour, who accused the Conservatives of having a "black hole" in their spending and taxation plans.
Opposition strategists believe the issue is returning to the centre-stage after the Northern Rock crisis and growing fears that the economy is cooling.
Mr Osborne sought to pin the blame for the growing uncertainty on Mr Brown for failing to "fix the roof when the sun was shining".
The shadow Chancellor said: "It is his economic incompetence and fiscal incontinence that have left Britain more exposed than any other developed economy to the current crisis."
He argued that Mr Brown's 11 budgets had left Britain with Europe's worst public finances. "The system of financial oversight he personally insisted on left Britain as the only country facing a run on the bank.
"His taxes and regulations have left the British economy more inflexible and less competitive."
Speaking at the London School of Economics, Mr Osborne said the rapid development of China and India had kept inflation low around the world.
"Our competitors used the fat years to prepare for the lean years. Britain did not," he said. "We are the least prepared country in the developed world to cope with the current financial turbulence."
He also took a swipe at Mr Brown's "very public dithering" over whether to reappoint Mervyn King as the Governor of the Bank of England.
"At a time of great uncertainty in financial markets, this is one bit of uncertainty we could all do with out," Mr Osborne said.
Andy Burnham, the Chief Secretary to the Treasury, retorted by claiming the shadow Chancellor had failed to produce "workable, thought-through solutions".
"Instead, he is once again promising lower borrowing, on top of massive tax cuts and dozens of unfunded spending pledges. The sums simply don't add up."