Doctor's research triggered a furore and was direct cause of slump in take-up of MMR, which has led to outbreaks of measles in some parts of the country

Andrew Wakefield, the doctor who claimed to have discovered a link between measles virus, bowel diseases and autism and thereby sparked widespread fear of the combined MMR jab, conducted unnecessary, invasive tests on children, the General Medical Council found today.

Branding him a dishonest, irresponsible doctor, the GMC disciplinary panel, which has sat and heard evidence for 148 days over two and a half years, finally found a long array of charges against him proven. But there were shouts of protest and dismay from the doctor's supporters.

Wakefield and two other doctors at the Royal Free hospital in London were brought before the GMC over the paper they published in February 1998 in the Lancet medical journal.

On the basis of case studies of just eight children, it suggested that measles virus might be linked to inflammatory bowel disease, which in turn might play a role in autistic spectrum disorder.

The paper conceded that the doctors had not found a definite link, but Wakefield, in a press conference, told the world he believed the measles, mumps and rubella vaccines in the MMR jab should not be given in one combined shot, but in single doses, preferably a year apart. It triggered a furore and was the direct cause of the major slump in take-up of MMR which has led to outbreaks of measles in some parts of the country.

The GMC found that Wakefield had flouted the rules in pursuit of his theory – and profit. At the centre of the case against him is the ethical conduct of the trial which resulted in the Lancet paper. The panel found he had subjected 11 children to invasive tests such as lumbar punctures and colonoscopies that they did not need, without ethical approval.

But investigations revealed more. In June 1997, before the paper was published, he filed a patent as one of the inventors of a vaccine for the elimination of measles virus and for the treatment of inflammatory bowel disease.

In February 1998, the same month as the Lancet paper, he applied for ethical permission to run a trial of a new potential measles vaccine and set up a company called Immunospecifics Biotechnologies Ltd which would produce and sell it. The father of one of the children he had seen with developmental problems and bowel disease would be the managing director. Wakefield tried out the new vaccine on the child, without mentioning it in the medical notes or telling the child's GP. He was also found to have unethically arranged for his son's friends to have blood samples taken from them during his birthday party – for which he paid them £5 each.

Wakefield hit on his theory after seeing children with bowel disease who also had developmental problems. The crucial third step in the hypothesis was the timing of the MMR vaccine: the first shot is given at around 18 months, which is also when autistic spectrum disorders start to be noticed.

In front of the GMC with him were two doctors who were at the time colleagues in the department of paediatric gastroenterology at the Royal Free, Prof John Walker-Smith and Dr (now Prof) Simon Murch. The GMC decided they shared responsibility for the ethical conduct of the trial, although neither one was said to have acted dishonestly.

The trial that Wakefield proposed troubled the ethics committee of the Royal Free. It is a fundamental principle in paediatrics that no child should be subjected to more than a blood test unless it is necessary for their treatment. But Wakefield proposed a barrage of invasive procedures. Dr Evan Harris, the Liberal Democrat spokesman who complained to the GMC, believes the committee should have sought advice from an independent paediatrician. Instead, it asked a gastroenterologist colleague of Wakefield.

The committee gave its conditional approval. The GMC panel decided that those conditions had been flouted – and that the trial had been unethical.

The GMC looked into the cases of eleven children who were entered into the trial. Many rules had been broken. Wakefield's contract was for "experimental gastroenterology" and he was not allowed to treat children, but he ordered tests and procedures that were not necessary for their health. In the interests of proving Wakefield's theory, children were given lumbar punctures in the spine, colonoscopies and barium meals – all significant procedures. Children were enrolled who did not fit the strict criteria for entry to the trial and they had not come from a GP who was referring them because they needed treatment.

Wakefield, now based in the US, has also been found not to have been open with the Lancet. He did not tell them that £55,000 funding for the study came from the legal aid board. Wakefield was advising Richard Barr, a solicitor who wanted evidence to sue the vaccine manufacturers on behalf of the parents of children with autism. It was a clear conflict of interest and should have been declared.

All three doctors will now come back before the panel in April, where the GMC will decide if they are guilty of serious professional misconduct, which could end in one or more of them being stripped of their licence to practise medicine.

Harris said Wakefield's reputation and that of his campaign was "in tatters and it is sad that it has taken so long for this to be demonstrated.

"That the GMC has found Wakefield guilty of unapproved and unnecessary invasive tests, including spinal taps, on young children, is the most damning indictment possible. The findings of failure to declare financial interest are a secondary consideration."

Dr Shona Hilton, of the Medical Research Council, said the scare had a huge impact on parents, undermining their trust in MMR vaccination. "Thankfully confidence is returning and the uptake of MMR vaccine is increasing," she said. "We need to continue rebuilding trust with parents that MMR vaccination is safe and ensure that those parents caring for children with autism do not blame themselves."

Wakefield, who was not at the hearing but spoke outside the GMC offices minutes after the ruling, said he was "extremely disappointed" by the outcome. He said: "The allegations against me and against my colleagues are both unfounded and unjust … and I invite anyone to examine the contents of these proceedings and come to their own conclusion."

He went on: "It remains for me to thank the parents whose commitment and loyalty has been extraordinary.

Thousands of people, mainly parents of autistic children, have continued to support Wakefield. Panel chairman Dr Surendra Kumar was heckled by parents as he delivered the verdicts in central London this afternoon. One woman shouted: "These doctors have not failed our children. You are outrageous."