The soaring cost of negligence now threatens to swallow up to a tenth of the entire health service budget.

Alarming figures revealed by the National Audit Office yesterday show the NHS faces a £5.89billion bill in cases it expects to lose. Further claims could add another £3.2billion compensation.

Health chiefs and ministers blame the growing 'compensation culture' in Britain. But patient groups say they are a signal that the NHS should stop blunders being made in the first place.

And while NHS staff are being encouraged to own up to mistakes as part of a 'no blame' culture, campaigners say patients are often driven to sue because of cover-ups.

The number of clinical negligence cases pending against the NHS has risen by more than a third between 2002 to 2003, from 7,628 to 12,173.

The NAO report said: The cost of clinical negligence claims is a significant drain on resources available for patient care.'

Simon Williams, of the Patients' Association, said: 'It is right that when something goes wrong, patients should be given compensation.

'However, there are a lot of people who are chancing it.

'When you go to a hospital it is amazing to see the number of adverts for legal firms.'