Helen Rickard and Michaela Willis are best friends for the worst imaginable reason. Their bond is born out of a terrible, mutual tragedy. Michaela's week-old son Daniel and Helen's 11-month-old daughter Samantha both died at the hands of paediatric heart surgeons at a hospital in Bristol.

In Helen's case the scandal has taken a double toll – her partner Andy, unable to cope with the loss of his daughter in 1992, committed suicide two years later.

Helen and Michaela put their sick children in the hands of doctors they trusted to make them well again. But Daniel and Samantha never survived the operations. There is no certainty they would have done had they received their care at a different hospital. But few doubt their chances would have been better.

Helen and Michaela met at the House of Commons in June 1996, where they began the fight for an inquiry into the paediatric cardiology unit at Bristol Royal Infirmary. A growing number of parents wanted to know how two surgeons, James Wisheart and Janardam Dhasmana, had been allowed to carry on operating on babies and children despite repeated warnings of high death rates.

On Wednesday the public inquiry into the tragedy will finally publish its report, more than two years after it began. Helen and Michaela, who have each received £20,000 compensation, will make another trip to London to discover its far-reaching and wide-ranging implications.

"Whatever they do it will never be enough," said Helen. "But I don't want to spend the rest of my life being eaten up by anger. I want to try to prevent this happening again."

Sitting in her kitchen in her terraced house in Bristol, two miles from the hospital where her daughter died, the tears well up in Helen's eyes. She has lost almost everything in the nine years since Mr Wisheart embarked upon a 12-hour operation, beyond his capabilities, to repair a hole in Samantha's heart.

Helen, now aged 34, remembers the last time she saw Samantha alive. Helen and Andy, her partner, carried her down to the operating theatre and laid her on the table. "She was just looking at me and holding her arms out and screaming," recalled Helen. That was 8am on 3 February 1992. By 6pm Samantha, aged 11 months, was dead. "I just started screaming over and over again. I had never contemplated her dying," she said. "My life went downhill from there on in."

Andy and Helen returned to the BRI six weeks later to see Mr Wisheart and discuss what happened. They told the surgeon he should not feel guilty and that they did not blame him for Samantha's death. They were not aware that knowing hospital staff had already dubbed the paediatric cardiac unit "the killing fields" and one ward "the departure lounge".

By the time the General Medical Council had struck off Mr Wisheart in 1998 for serious professional misconduct, Helen, in front of television cameras, was branding him "evil".

In the intervening time, Andy at the age of 26 had committed suicide by placing a bag over his head in the living room. The birth of a second child, Ben, now aged eight, was not enough to keep Andy going.

"Andy had lost the person he was most in love with. They were just besotted with each other and he couldn't protect her and he couldn't prevent her dying," said Helen. Their own relationship had also begun to disintegrate. "People have this strange idea you can support each other. But how can you lean on somebody who is already bent double in their own agony? The pain was so great we were completely unable to share it with each other."

Over the years the truth began to emerge. Helen was told the success rate for hole-in-the-heart operations was 75 per cent. That was true nationally. At Bristol the survival chances were considerably lower. Reports into the surgeons' performances had been hushed up; Dr John Roylance, then head of United Bristol Healthcare NHS Trust, was also struck off for failing to stop the operations.

"I was furious I had been lied to. People knew what was going on in Bristol. But nobody told the parents of the children. It was privileged information and the people entitled to it were people like me and other parents," said Helen. "How dare I be lied to and my daughter operated on in a place where it feels like she was sentenced to death. I feel betrayed by them; let down. I am disgusted by them. They have the medical knowledge but in terms of my child I know best."

Daniel Willis, born on 18 May 1993 in North Devon District Hospital, was 12 hours old when doctors noticed he was turning blue. A week later he was being operated on by Mr Dhasmana at Bristol Royal Infirmary. The arterial switch operation has an 80 to 85 per cent success rate nationally but Daniel was Mr Dhasmana's ninth arterial switch operation, says Michaela, and six had died.

"We treated Dhasmana like God. He was giving us a chance and saving our child," said Michaela, who lives with her husband Steve and three children in north Devon. "That is the hurtful part about it. If I was in that position I could not watch children die time and time again. Private Eye had called it the 'killing fields' and a year after that my son was operated on. Why didn't anybody do anything about it?"

Michaela, now aged 33, believes she has finally come to terms with Daniel's death after eight years. Wednesday's report will be the culmination of years of campaigning for a full investigation. "We cannot change the past but we can make a difference to the future," she said. "The report should have come out quickly but now we are having to go back to something that is really painful, and there is no way you can avoid it. I will just be glad when it is over once and for all."