Parents of children who died on a cardiac ward have slammed an independent review into the hospital which cared for them as a "cover-up and a whitewash".
The review found families were let down by Bristol Royal Hospital for Children, with low staffing levels meaning a ward was under strain and youngsters put at risk.
It made 32 recommendations for University Hospitals Bristol NHS Foundation Trust, NHS England and the Department of Health.
These include that a national review of paediatric intensive care services should take place and conversations with clinicians should be recorded.
Following the review, NHS England said major changes in the way heart services are provided across the country would be announced next week.
Sean Turner died aged four in March 2012 from a brain haemorrhage after previously suffering a cardiac arrest while on the hospital's Ward 32 following complex heart surgery.
His mother Yolanda Turner, 48, criticised the review and an independent report into his care - one of 27 commissioned for children cared for by the hospital.
"I don't think it has gone far enough," Mrs Turner, a foster carer from Warminster, Wiltshire, said.
Certainly within Sean's own report there are areas we feel that the review has not gone far enough, they have not been brave enough to really properly investigate.
"We still feel there are areas that are whitewashed over, ignored, it's disappointing.
"A lot of the families are unhappy with their personal reports, they are all very upset with their personal reports, feel it's a cover-up, feel it's a whitewash."
Luke Jenkins died aged seven in 2012 after undergoing heart surgery at the hospital.
His father Stephen, 33, from St Mellons, Cardiff, described the review as "very poor" and Luke's individual report as "really weak".
"We didn't expect it to be just a paper exercise. I wanted something to come out of it that holds someone to account," Mr Jenkins said.
"Luke died because of this. This review has been started because of Luke and Sean - has it been a waste of time and them saying 'let's tick the boxes and move forward'?
"We want the place to be safer for children to go there and not experience what we experienced. We were hoping this was going to be the end of it but it seems we have to go on fighting."
The review was commissioned by NHS England Medical Director Sir Bruce Keogh in 2014 and involved 237 families whose children were treated by the hospital.
Ten are taking legal action against the trust, including seven whose children died after treatment on Ward 32 - the principal focus of the review.
Chair Eleanor Grey QC said there was no evidence to suggest failings in care and treatment of the nature identified in the Bristol Public Inquiry of 1998-2001.
Outcomes of care at the hospital were "broadly comparable" with those of other centres caring for children with congenital heart disease, she said.
However, the barrister added: "The ward that the children were cared for, that's Ward 32, in that period from 2010 to 2012 was routinely under strain.
"The nursing numbers would have fallen below the recommended levels on a reasonably frequent basis. We felt that children were put at risk of harm as result.
"We felt that the risks in that period were not adequately assessed and weren't reported to senior management and the board.
"That was a serious failing in governance."
When asked whether deaths could have been prevented, she replied: "The language I am using is 'risk of harm' and 'poor care'."
The review found senior managers failed to respond to parents' concerns and were defensive after a warning notice was issued in 2012 following an unannounced Care Quality Commission inspection.
Professor Sir Mike Richards, chief inspector of hospitals, said a separate review by the CQC had "no significant criticisms of any individual child's care".
The trust's care has been assessed as safe and effective, with the latest CQC inspection rating children's heart services as good.
Robert Woolley, chief executive of the trust, said the findings of the independent and CQC reviews were fully accepted.
"We are deeply sorry for the things we got wrong - for when our care fell below acceptable standards, for not supporting some families as well as we could have and for not always learning adequately from our mistakes," he said.
"This undoubtedly added to the distress of families at an already very upsetting time for them.
"We didn't get it right for these families, and I'd like to apologise to the families unreservedly, on behalf of everyone at the Trust."
He said the review found evidence of "really good care" and acknowledged "substantial improvements" that had been made.