Professor Ian Kennedy chairs the inquiry

This is due to deliver its final report early in the New Year.

The overview of statistical evidence, published on Thursday, found between 30 and 35 "excess deaths" at Bristol between 1991 and 1995.

The experts found that as mortality rates fell dramatically in paediatric heart surgery during the 1980s and 1990s elsewhere in the country, but not at Bristol.

Another portion of the report suggested mistakes had been made in the overall care of 10% of babies and children sent to Bristol for heart surgery.

Point the finger

Some of these were judged to be bad enough to have probably had an impact on the outcome for the child, while the remainder, experts decided, could have had an effect, but they could not be as certain.

But despite these figures, the statistical experts are unwilling to point the finger directly at the surgeons.

Maria Shortis founded an influential parents' pressure group

The report says: "We must stress that this does not necessarily imply that there was poor performance by individual surgeons.

"The whole system of care provided for these children, from diagnosis and referral through to post-operative care and discharge needs to be examined to look for an explanation for the observed poor performance."

A detailed look at 100 operations found far more potentially-serious errors in pre operation and post-operation care than actually during the operation itself.

In fact, there were only two operations in which the expert assessors thought that poor surgical performance was reasonably likely to have had a bad effect on the outcome.

Maria Shortis, now a director of the pressure group Constructive Dialogue for Clinical Accountability, said: "It is important to remember that there are many instances in which individual clinicians and their decisions are implicated - however this report is thorough and should be welcomed.

"It should be accepted that no hospital would be completely without some episodes of sub-optimal care"

James Wisheart

"It would be interesting to see what would happen if you examined other hospitals in the way Bristol has been examined."

Mr Wisheart, who had retired before being struck off, said many of the sources of figures used by the inquiry to judge Bristol were flawed, and made events at the hospital seem much worse than was the case.

He told BBC News Online: "Obviously, one would not want the figures to be that high, but it should be remembered that no one knows what would be found in other hospitals, as such a review has never been carried out before; I doubt whether any hospital would be completely free of some episodes of sub-optimal care.

"The reviews show that if there are shortcomings at Bristol that are greater than would be expected, they involve care across the board, including the surgeons - but not only the surgeons."