Up to 10 families are believed to be taking legal action against a hospital over its treatment of newborn babies and young children who died or suffered complications during treatment.
University Hospitals Bristol NHS Foundation Trust is accused of a catalogue of neglect and mistreatment of babies and children with heart problems, over a four-year period from 2008.
The claim is thought to centre on up to 10 families - including seven whose children died following treatment at the hospital. Previously, some had spoken out about the "inept care" of the young patients, calling for a public inquiry into what they considered to be "chronically low standards".
The hospital, Bristol Royal Hospital for Children, has defended its mortality record. However, claims in the Sunday press that the hospital is being sued could further underline fragile confidence in sections of the NHS, following this week's damning report into failings of care at Stafford Hospital.
Warminster couple Stephen and Yolanda Turner claim their son Sean's case is not isolated and urged other parents to come forward with their own stories.
Sean, four, died of a brain haemorrhage last March after previously suffering a cardiac arrest while on the ward. His death at the hospital came six weeks after he underwent vital corrective heart surgery.
"All we want is the truth," Mr Turner said following his son's death.
"After the nightmare we lived through with Sean we deserve nothing less than the truth. That is vitally important for other families as well.
"Other families should not have to suffer what we suffered. This shouldn't be swept under the carpet and forgotten and things left to go on unchanged."
The couple claim they pleaded for Sean to be returned to intensive care as his condition worsened.
They later hit out in an official letter of complaint which lists a host of shortcomings regarding their son's care.
They claim ward hygiene was poor, staff were incompetent and that Sean was neglected to the point where he had an avoidable cardiac arrest.
They came forward publicly after being struck by the similarities of Sean's death to an earlier tragedy - Cardiff youngster Luke Jenkins, seven, was expected to make a full recovery after successful corrective surgery at the hospital, but died after suffering a cardiac arrest on a bank holiday within a week of his operation.
His heart stopped for 43 minutes before he was resuscitated, after which he underwent exploratory surgery. He died the following day.
His death was due in part to the duty surgeon having to be urgently called in from home on Good Friday when Luke collapsed, something admitted by hospital bosses.
Junior nursing staff lost vital time because they did not know where resuscitation equipment was kept, it later emerged.
The emergency team was also unfamiliar with the equipment because cardiac arrest was rare in the ward environment, the hospital claimed.
In both cases the children were transferred from the intensive care unit to Ward 32 too rapidly, according to their parents.
Both sets of relatives believe that, but for substandard after-surgery care on the ward, their children would be alive.
Both claim that once on the ward they were increasingly anxious at the reduced level of care they felt their children received.
In both cases rising concerns were dismissed by ward staff who appeared too busy and too few to care properly for patients.
The Turners also say that in Sean's case, staff could not claim ignorance of where to find and how to use emergency equipment. Their son suffered a cardiac arrest, and survived, on the ward weeks before Luke's death.
Robert Woolley, foundation trust chief executive, said paediatric cardiac surgery carries "significant risk" but that these are explained to parents.
He said: "Despite these risks and the complex needs of the children we care for, we have results among the best in England.
"A comparative outcomes assessment for 2000-2008 undertaken as part of a recent Safe and Sustainable review showed that the Bristol service has the third best mortality rates when mortality rates are compared between the eleven current surgical centres in England.
"Mortality figures for 2007- 2010 show that the Bristol centre had a 1.6 per cent mortality rate for surgical procedures in the under one year age group and 1 per cent in the one to 15 year old age group.
"Since 2009, a national review of children's congenital heart services has taken place which rigorously assessed the quality of care in existing centres. In July 2012, it was announced that the Bristol children's hospital will be designated as one of seven specialist surgical centres in England."
A spokesman for the trust was unable to confirm the status of legal proceedings.