Outstanding medical negligence claims against the NHS could cost the cash-strapped service up to £2.8bn, a Commons report warns.

The money lost annually would more than pay for the pledge by Prime Minister Tony Blair to bring UK health spending up to that in other European states - a target estimated to cost about £2bn a year.

MPs warn that negligence is just one problem in a service beset by financial difficulties, including widespread fraud.

The Public Accounts Committee says that negligence cases could divert already scarce resources away from a service struggling to cope with winter pressures.

In their report, the MPs say: "We are appalled that there are at least 15,000 cases of clinical negligence on the NHS books, and that there may be far more.

"These cases represent a tragedy for the people involved.

"And the level of outstanding liabilities, which may be as high as £2.8bn, is a significant drain on stretched health care resources."

The cross-party committee criticised the lack of financial control in the NHS, and the level of fraud in the system.

The report says the NHS has made "significant" savings in recent years.

But it adds: "We found too much evidence that the service's financial affairs had not been handled well.

"They must do better than this, by developing their staff's skills or bringing in more external expertise.

"The level of detected fraud in the system is very low, around £2.6m, compared to the stock of fraud in the system, which exceeds £150m.

"And where fraud has been detected, few prosecutions have resulted and recoveries have been small."

One example of fraud highlighted by the report is the phenomenon of "ghost patients".

These are patients included on GPs' lists who either do not exist, have moved away, or who are treated by other doctors. GPs can claim a fee for each patient that is registered on their list.

The report finds that there were about 2m more patients registered with GPs in England than there were residents in the country. About 1.75m registrations were for people who had changed addresses.

On efficiency, it found that there were still "significant" variations in the cost of treatment such as hip replacement operations across the country.

The report said: "The potential gains are enormous - up to a 12% reduction in unit costs - if all NHS Trusts performed at the level of the most efficient."

Tory MP David Davis, committee chairman, said that in recent weeks it had been "all too clear" that the NHS faced considerable and continuing financial pressures.

He said: "Whilst I welcome the improvement in financial performance in the NHS, standards of financial management still leave a lot to be desired.

"There is considerable scope to bring the standards of the worst health bodies up to those of the best by targeting the poor performers and upgrading and spreading good practice.

"Improving efficiency and financial management, and reducing the drain from fraud and clinical negligence, would release precious resources that could be directed towards patient care."