Harry Trusted, a representative of the Bristol Heart Children's Action Group, said detailed statistical evidence showed dozens of children may have survived if they had been treated elsewhere.

We will never know exactly how many children died at Bristol because of mismanagement and bad care

Harry Trusted, Bristol Heart Children's Action Group

Mr Trusted was giving evidence to the public inquiry into high deaths among children who underwent cardiac surgery at the hospital.

He said: "We will never know exactly how many children died at Bristol because of mismanagement and bad care.

"We think with confidence the figure is probably between 50 and 100 and in our submission that in itself is justification for this inquiry.

"The events this inquiry is looking into may properly be described as a tragedy."

Mr Trusted said Bristol had failed in a number of areas including the competence of the surgeons themselves.

He was also scathing about the lack of action by a range of individuals and agencies once it became clear there were problems in Bristol.

He blamed this on a culture which was "closed, secretive and defensive".

Peter Skelton, also for the action group, called for a radical overhaul of the rules on the removal and retention of dead children's organs.

Press attacked

It is clear to me that a substantial number of parents and children did not receive the standard of care that they were entitled to expect

Hugh Ross, chief executive, United Bristol Healthcare NHS Trust

For the Bristol Surgeon's Support Group, Mr Christopher Sharpe QC said the surgeons involved had dedicated their lives to the children they cared for.

He launched a scathing attack on the press reporting of the inquiry.

In a written submission, Hugh Ross, the current chief executive of the United Bristol Healthcare NHS Trust (UBHT), which runs the Bristol Royal Infirmary, apologised for the scandal.

He said: "It is clear to me that a substantial number of parents and children did not receive the standard of care that they were entitled to expect."

The public inquiry, which is about to conclude the first phase of its investigation, has now examined around 2,000 cases.

The General Medical Council originally investigated operations on 53 children, of whom 29 died and four were left brain damaged.

Dr John Roylance, the former chief executive of the UBHT, and cardiac surgeon Mr James Wisheart were struck off by the GMC.

Cardiac surgeon Mr Janardan Dhasmana was barred from operating on children for three years.

The multi-million pound inquiry is due to complete its work and issue a report later this year.