For some, Professor David Southall is a pioneer who has devoted his life to protecting children from abuse; for others he is an "arrogant menace" who has destroyed families and ruined lives in pursuit of his own personal aggrandisement.

He has divided public and professional opinion like no other researcher in recent years, but this judgment may mark the beginning of the end of his controversial career.

Separated from his second wife and forced to put his house up for sale, his downfall has been spectacular. For years, his word was accepted as gospel by courts and social workers investigating cases in which parents were accused of abusing their own children.

He qualified in 1971 and, as a young researcher of 29, wrote a well-received paper on cot death and babies with breathing difficulties. His research was the start of his interest in paediatrics and child protection. By 1986, he was an acknowledged expert in child protection and rare illnesses among babies.

Along with Professor Sir Roy Meadow, who is also facing a GMC inquiry over evidence in civil and court cases, Professor Southall propagated the theory of Munchausen's Syndrome by Proxy (MSbP). The condition, they said, drove parents - mainly women - to harm their own children in a bid for attention.

The theory became an obsession. Professor Southall's first brush with controversy came in the 1980s, when he pioneered the use of covert video surveillance (CVS) to film parents he suspected of abusing their children while they were in hospital. The films showed parents breaking their children's bones and smothering and poisoning their babies.

The tapes led to 33 women being convicted, but also divided doctors and parents over the ethics of filming people without their consent. Professor Southall said CVS should be used "whenever appropriate". He was suspended in 1999 by his hospital in North Staffordshire after complaints from parents over his research on babies and breathing difficulties. The study involved placing premature babies in a low-pressure tank and forcing their lungs to expand to take in air. Twenty-eight children who took part died and 15 were brain-damaged. Parents complained that they were not told of the risks and that they had not given informed consent. After an investigation that lasted two years, Professor Southall was cleared and reinstated. He was awarded an OBE in 1999 and was considered to be one of the leading expert witnesses in criminal cases on abuse. He was seen as "juror-friendly" with his simple evidence and absolute conviction in his own judgements.

But the acquittal of Sally Clark raised questions about the nature of his research and the way in which he gave evidence. The case has proved to be his nemesis, with the publicity prompting the seven other complainants to come forward.

Richard Tyson, counsel for Steve Clark in the GMC case, told the PCC hearing that Professor Southall was arrogant and dogmatic. "He still thinks he is right," said Mr Tyson. "A doctor who has no insight, who arrogantly continues to believe that he is right, is a very dangerous doctor."

Davina McLean, whom Professor Southall also accused of suffering from MSbP, said she felt like she was "being raped across the table" by his allegations. Steve Clark has described his accuser as a "menace".

Professor Southall still divides opinion. During the GMC case, 85 people wrote glowing testimonials supporting him, including surgeons, nurses, social workers and a judge. David Hall, professor of community paediatrics at the University of Sheffield, said: "He is a pioneer. David Southall is totally committed. We need people like him who challenge received wisdom."

Yesterday, Professor Southall insisted he wanted to continue working with children. As he walked away from the tribunal building in Manchester, one aggrieved parent shouted: "It's not over." In the case of Professor Southall, that is probably true.