As an eminent consultant paediatrician, Professor David Southall was known for his pioneering work with young patients.

The 58-year-old made his name by using covert video surveillance to identify children at risk of abuse.

As a consultant paediatrician at University Hospital of North Staffordshire NHS Trust, which runs hospitals in Stoke-on-Trent, Prof Southall found children aged between two and 44 months were being deliberately injured by parents or step-parents while in hospital.

Following the eight-year study, which began in 1986, he claimed 23 parents of the 39 children suffered from attention-seeking disorder Munchausen's Syndrome by Proxy.

Prof Southall's controversial study raised difficult ethical issues and sparked an angry response from parents, as 33 were prosecuted after his findings were passed to the police.

But cracks in his career began to appear in 1998, following concerns over a bizarre experiment testing a link between cot death and air travel.

Parents were told babies in the study, aged on average three months, faced a "small risk of sudden death" when given air with 15 per cent oxygen compared with 20 per cent in normal air. Despite more protests over the inherent dangers, the controversial ventilator tank experiments on premature babies continued, even though 28 of the babies involved in the project died.

Prof Southall was suspended in 2000 while an inquiry into his work was carried out, but he was reinstated in 2002 after being cleared of any professional misconduct or incompetence.

But it would be his reaction to a Channel 4 Dispatches documentary, broadcast in April 2000, into the circumstances surrounding the sudden deaths of Sally Clark's two sons, Christopher and Harry, that would seal his notoriety.

The solicitor was jailed for life for the murder of the boys, but was released in January 2003 after the Court of Appeal quashed her conviction.

Prof Southall said he believed "beyond all reasonable doubt" that Mrs Clark's husband Steve had murdered their sons.

After a two-day hearing in August 2004, Prof Southall was found guilty of serious professional misconduct and banned from engaging in any aspect of child protection work within or outside the NHS for three years.

He has effectively been working under a ban since his suspension from University Hospital of North Staffordshire, when complaints were first lodged with the GMC.