Many hospitals that appeared to have delivered a poor service under the new clinical indicators have dismissed the figures as inaccurate and misleading.

One example shows just how difficult it can be to make comparisons between different hospitals, even by the apparently simplest measure.

Weston Park Hospital in Sheffield, a specialist cancer centre which treats many patients in the terminal stages of their illness, has a high number of patients who die shortly after emergency surgery.

However, the hospital does not carry out a single operation.

However, the NHS classes the insertion of a bladder catheter, a frequent treatment to ease the suffering of very ill patients, as surgery.

So when those patients die from cancer shortly after this "emergency operation", the figures start mounting against Weston Park.

The headline death rate - of 16,753.1 deaths per 100,000 patients - is bound to alarm patients.

Dr Ian Manifold, the hospital's director, said: "All the returns have been developed for larger, general hospitals, not specialised hospitals.

"We are plagued by this sort of thing all the time, and it's something we will have to talk to the patients about if they ask."

Bristol under the spotlight

United Bristol Healthcare Trust (UBHT) - which runs the Bristol Royal Infirmary, the hospital at the centre of the heart babies scandal which led to two doctors being struck off and another sacked - recorded a high figure for the number of patients who were re-admitted within 28 days of discharge.

But hospital chief executive Hugh Ross said the figure was artificially inflated because it included patients who were transferred from the care of one consultant to another specialist within the hospital.

"This transfer of care between two consultants was shown as a re-admission when in fact, it was part of a continuing stay in hospital; thus appearing at least twice.

"Transferring patients between specialists reflects the large number of complex cases treated by UBHT, such as multiple injuries and elderly frail people with several serious problems."

St George's figures misleading

Professor Paul Jones says the figures are misleading

St George's Hospital, London, has the worst death rate following non-emergency surgery for any teaching hospital in England. The indicators show that one in a hundred patients die, four times the national average.

However, St George's medical director Professor Paul Jones said the figures were misleading, and that the hospital actually had an average death rate.

He said: "When we looked into our figures we realised that we have counted our high risk patients that have come in from other hospitals specially to St Georges for operations that cannot be done in their local hospitals.

"That has made our figures look very bad, and we believe that is the sole reason for why our figures look much worse - we have included very sick patients whereas other hospitals have counted their patients differently."

Salford defends record

Salford Royal Hospitals NHS Trust recorded one of the highest rates of deaths within 30 days of surgery following emergency admission - 6,000 deaths per 100,000 admissions.

However a spokesman for the hospital dismissed the figure as a "statistical artefact".

He said: "The Regional Office of the NHS Executive have told us their view is that the calculation is grossly misleading.

"One person in the 10-14 age group was treated and subsequently died.

"Due to the age standardisation, this resulted in a 100% death rate in this age band, resulting in a statistical skew to the data.

"This is clearly a statistical artefact, and is not necessarily indicative of poor service provision."

'We wanted data withdrawn'

Northern Devon NHS Healthcare Trust registered high rates both of numbers of patients who died within 30 days of emergency admission with a broken hip, and of numbers of patients who died within 30 days of emergency surgery.

However, chief executive Frank O'Sullivan said the calculations were completely flawed for every indicator.

For instance, the hospital completed 5,168 planned operations during the year, but its final figure was calculated on the assumption that they had only carried out 160 operations. This generated a death rate 30 times higher than reality.

"In principle we have no problem with clinical indicators, but the information has to be accurate," said Mr O'Sullivan.

"We asked that the data for our trust be withdrawn as it was quite clearly flawed, and could effect the credibility, not only of our trust, but of the whole exercise."