The doctor who accused Sally Clark's husband of murdering their two sons abused his professional position, the General Medical Council has ruled.
Professor Southall denied serious professional misconduct
Professor David Southall accused Steve Clark of the murders on the basis of a TV documentary. Mrs Clark was jailed and later cleared of killing the boys.
A GMC panel ruled that Professor Southall's actions were "inappropriate", "irresponsible" and "misleading".
It will decide in August whether he should be struck off.
Sally Clark was convicted in 1999 of murdering her two sons Christopher and Harry.
But that conviction was quashed when new medical evidence showing the babies died of natural causes was accepted at a second appeal hearing in January 2003.
The GMC hearing centred around conclusions Professor Southall drew after seeing an interview with Mr Clark on Channel 4's Dispatches programme broadcast in April 2000.
In his interview, Mr Clark described how the couple's first baby Christopher had suffered a nosebleed just 10 days before he died in December 1996.
Professor Southall told police he believed Mr Clark had killed the children after watching the interview.
He later outlined his concerns in a report. It was submitted to the family court, which was considering who should take care of the Clark's third child.
Professor Southall drew up his report even though he had no access to case papers, medical records or post mortem results.
Sally Clark was cleared of murdering her two sons
He did not interview Steve or Sally Clark before submitting the report.
The GMC panel's criticisms centred around Professor Southall's decision to write a report on the family.
The paediatrician had defended his actions during the seven-day hearing and denied serious professional misconduct. He also said that he still believed Mr Clark may have killed his two sons.
Mr Clark, who lodged the complaint against the professor, told the GMC hearing last week that he had thought the allegations against him were a "sick joke".
The chairman of the GMC panel had criticised Professor Southall at the hearing on Tuesday.
Professor Dennis McDevitt said Professor Southall should have told the authorities of his concerns that Mr Clark could have killed his sons.
But he said "everything beyond that seems to be a quantum leap".
Mike Mackay, the Clark family solicitor, said Steve would be happy with the GMC ruling.
"He will be very pleased that at last this part of the proceedings has been concluded after four years," he told the BBC.
Professor Southall, based at North Staffordshire Hospital in Stoke, is one of Britain's leading experts on Munchausen's Syndrome By Proxy, a condition which apparently drives parents to harm their own children in order to win attention.