By Adam Brimelow
BBC News health correspondent
The negligence bill is set to increase
Clinical negligence payouts by the NHS in England are expected to rise by 80% next year.
Trusts have set aside £713m to cover costs, up from about £400m this year, figures obtained by the Tories show.
Shadow health minister Mark Simmonds said the payments would have a severe impact on hospital budgets.
But the government insists the payouts, which have increased partly because of changes in the way cost of care is calculated, are "fully covered".
The NHS litigation authority collects money every winter from health trusts to cover expected clinical negligence payouts.
According to the Conservatives, the £313m estimated increase in payouts will eat up almost a third of the additional funding that hospitals will receive next year.
Steve Walker, chief executive of the NHS Litigation Authority, said part of the increase was prompted by a recent ruling in the Court of Appeal - the Thompstone judgement - which changes the way that payments for care are calculated.
He also said the move to more "no win no fee" cases had increased costs "dramatically" because it meant that solicitors were picking their cases carefully.
"The proportion of successful claims has gone up and is rising," he said.
"Legal practices are businesses and why not try and double your income for the same amount of work."
Mr Simmonds said the NHS needed a robust and fair system to enable patients who had received negligent treatment to get the compensation they deserved.
"Instead, we have an inefficient system which incurs vast legal costs for NHS trusts involved in legal battles."
Nigel Edwards, director of policy at the NHS Confederation, said: "There should be enough money in the system to pay, though some trusts are reporting a shortfall."
More than half of the total payouts are for maternity-related cases.
Under the government's maternity strategy, these services are supposed to receive extra funding, but the Conservatives say the money is being "eaten up" by negligence claims.
Professor Cathy Warwick, general secretary of the Royal College of Midwives, said: "A properly funded maternity service is likely to lead to clinical negligence claims dropping."
She acknowledged that the Department of Health had started to increase the money going into maternity care.
But she added: "It is critical that this money contributes to the development of a high quality service with a view to reducing clinical negligence claims."
Dr Karen Roberts, of the doctors' insurance body the Medical Defence Union, said: "Of course, claimants who have been negligently harmed by their doctor should be compensated, but a system that provides solicitors' firms with rewards which dwarf the value of a claim needs to be reformed."
A spokesman for the Department of Health insisted that the anticipated increase in clinical negligence payments had been fully funded and that "there is no black hole."
He added: "The premium collected in 2009/10 is substantially higher than previous years because of delayed settlement of more than 100 high-value cases, as well as other factors, such as rising legal costs.
"We fully expect this figure to fall back to historical levels in 2010/11."