The pathologist who first ruled that newspaper seller Ian Tomlinson died from natural causes at the G20 protest was yesterday found to have behaved "irresponsibly" in other post-mortem examinations.

A General Medical Council disciplinary panel said Dr Freddy Patel, 63, failed to identify marks on the body of a five-year-old girl which suggested she had been violently attacked prior to her death.

The panel's chairman, Richard Davies, said Dr Patel's report into the death of the five-year-old girl, who was admitted to hospital with a head injury following what was said to be a "serious fall", gave no details of so-called "marks of violence". His report said there were no "significant" marks of violence, which, Dr Patel told the panel, meant there were no marks relevant to the child's death. But the panel was shown evidence of marks which had been visible to the naked eye but which Dr Patel did not identify in his report.

Mr Davies said the panel considered it "probable" that Dr Patel "performed only a cursory external examination of the body". The panel added Dr Patel's conduct was "irresponsible" and not of the standard expected of a Home Office pathologist.

In another case, Dr Patel changed the details of woman's cause of death. He carried out a post-mortem examination on 5 January 2005, and decided she had died due to a blood clot in the coronary arteries. A month later, following a second post-mortem examination by another pathologist, he prepared an addendum to his report changing the cause of death to a brain haemorrhage in line with the new findings.

The panel said he had not adequately explained his reasons for the alteration and it was not persuaded that it had been "professionally scrupulous" to do so.

In a third case the panel found that Dr Patel had also failed to meet professional standards when he carried out a post-mortem examination on a four-week-old baby in August 2003. He did not obtain full skeletal X-rays prior to the examination as recommended by the Royal College of Pathologists' guidelines. The panel said the possibility of injury could not be excluded and it would have been "reasonable and appropriate" at that stage to give consideration to the possibility that the death might have been suspicious.

Dr Patel could be struck off if the panel finds his behaviour amounted to misconduct. He has already been suspended from the Home Office register of forensic pathologists amid questions about his post-mortem examination of Mr Tomlinson. The 47-year-old newspaper seller died during London's G20 riots in April last year after being pushed to the ground by a police officer. Dr Patel's competency was called into question after two other pathologists agreed that Mr Tomlinson died as a result of internal bleeding after falling on his elbow.

Mr Tomlinson's family said: "This raises the most serious questions about how and why Freddy Patel's appointment to carry out the vital first post-mortem on Ian could have been approved by the City of London Police. We demand answers."