The doctor who sparked the MMR controversy "showed a callous disregard" for the suffering of children and "abused his position of trust", a disciplinary panel ruled today.
Dr Andrew Wakefield's conduct brought the medical profession "into disrepute" after he took blood samples from youngsters at his son's birthday party in return for payments of £5.
The doctor, who was absent from today's General Medical Council (GMC) hearing, faces being struck off the medical register.
The panel decided the allegations against him could amount to serious professional misconduct, which will be decided at a later date.
Panel chairman Dr Surendra Kumar was heckled by distraught parents who support Dr Wakefield as he delivered the verdicts.
One woman shouted: "These doctors have not failed our children. You are outrageous."
She called the panel of experts "b*******" and accused the GMC of being a "kangaroo court".
Another shouted: "This is a set-up."
The GMC also found today that Dr Wakefield "failed in his duties as a responsible consultant" and went against the interests of children in his care in conducting research.
He further acted dishonestly and was misleading and irresponsible in the way he described a study which was later published in The Lancet medical journal, the GMC said.
In the late 1990s, Dr Wakefield and two other doctors said they believed they had uncovered a link between the MMR jab, bowel disease and autism.
The research sparked a massive drop in the number of children given the triple jab for measles, mumps and rubella.
The hearing has sat for 148 days over a two-and-a-half year period.
A total of 36 witnesses gave evidence at the hearing, which has reportedly cost more than £1 million.
A defiant Dr Wakefield said he was dismayed at the panel's decision.
He told reporters: "I am extremely disappointed by the outcome of today's proceedings.
"The allegations against me and against my colleagues are both unfounded and unjust - I repeated unfounded and unjust - and I invite anyone to examine the contents of these proceedings and come to their own conclusion."
He said on a personal note he was "dismayed" that two of his colleagues had been "dragged through this process".
He went on: "It remains for me to thank the parents whose commitment and loyalty has been extraordinary.
"I want to reassure them that science will continue in earnest."
He also thanked his family, supporters and legal team for their "enormous help".
Dr Wakefield was not at the hearing as the panel's decision was announced.
But later he emerged from the central London GMC offices to make the statement, surrounded by supporters who waved placards and chanted: "For he's a jolly good fellow."
The GMC said the doctor took blood samples from youngsters at his son's birthday party in the late 1990s and then laughed about it during a US presentation in March 1999.
Dr Kumar said of Dr Wakefield's case: "Despite your explanation that you did not consider it unethical to obtain blood in this way, the panel found that it was unethical and that you did not have ethical approval for such an undertaking.
"It also found that you caused blood to be taken in an inappropriate social setting and you showed a callous disregard for the distress and pain you knew or ought to have known the children involved might suffer.
"You abused your position of trust as a medical practitioner."
Dr Kumar said Dr Wakefield's conduct at the US seminar "was such as to bring the medical profession into disrepute".
The panel said his conduct was unethical and that Dr Wakefield did not have ethical approval.
Dr Wakefield was an honorary consultant in experimental gastroenterology at the Royal Free Hospital in London at the time of his research.
He and two colleagues involved in the research, professors John Walker-Smith and Simon Murch, who are also being investigated by the GMC, deny all the charges against them.
The panel also ruled today that Dr Wakefield submitted an application for funding from the Legal Aid Board but failed to disclose that some of the costs would have been met by the NHS anyway.
A charity which supports MMR warned there could be a new outbreak of rubella if uptake of the vaccine falls.
The disease can cause babies to be born deaf and blind if their mothers are exposed to it during pregnancy.
Joff McGill, information and research director for Sense, the national deaf-blind and rubella association, said: "This story is about more than Dr Wakefield, but the millions of children who have not been vaccinated since his theories first emerged.
"We need to get the message to all parents that to protect your children and others against rubella it is critical we stop the disease circulating.
"The only way to do this is by ensuring we have a comprehensive MMR vaccination programme for all children.
"The MMR vaccination remains the best and safest way to ensure we protect our children from the possible effects of these terrible diseases."
In respect of children involved in The Lancet research, Dr Wakefield, whose contract prevented him from carrying out clinical research on youngsters, was found not to have acted in their best clinical interests.
He ordered some youngsters to undergo unnecessary colonoscopies, barium meals, blood and urine tests and brain scans.
Some of the tests were carried out by Profs Walker-Smith and Murch.
The GMC said the children did not meet the criteria for inclusion in the research and that the doctors did not have ethical approval to investigate them.
The GMC panel said Dr Wakefield's actions in relation to the Legal Aid money were "dishonest" and that he knew that some or most of the funds would not be used for the reasons he had set out.
However, it said he did not use the money for his personal gain and it was spent on research.
The GMC also said Dr Wakefield's conduct in relation to how The Lancet research was presented was dishonest and irresponsible.
Dr Wakefield and Profs Walker-Smith and Murch will now be the subject of further investigation.
The panel found that the conduct of all three was sufficient to lead to a possible guilty verdict of serious professional misconduct.
A decision on that aspect, and any sanctions, is not expected for a matter of months.