A Dutch-trained doctor, found guilty of treating multiple sclerosis patients with stem cells from cows, could be struck off by the General Medical Council of the UK.
A GMC hearing has found his fitness to practise was impaired and that he breached "good medical practice".
It will decide later this month whether to remove him from the medical register or impose a lesser penalty.
The GMC panel said Dr Trossel had exaggerated the benefits of treatment based on "anecdotal and aspirational information".
The doctor was found to have offered treatments which were "unjustifiable" on the basis of evidence, inappropriate, not in the best interests of patients and were "exploitative of vulnerable patients."
He also failed to warn of potential risks, according to the panel.
It also found that Dr Trossel failed to respect the rights of patients to be fully informed and that he "abused" his position as a doctor.
Nine men and women, most suffering from incurable conditions, visited Dr Robert Trossel, "desperate" to find relief for their disease and prepared to raise large sums of money to fund their therapy. Back in April this year the council ruled that Dr. Robert Trossel "abused his position" when he subjected desperate MS sufferers to painful and expensive injections not designed for human use at his clinic in Rotterdam, Holland.
In many instances, Trossel told patients they were receiving umbilical cord stem cells when in reality he was using stems cells of animal origin, according to the report.
But he was not found to be dishonest because the panel accepted the doctor believed the claims he made.
It had heard, after a previous hearing that the doctor had experienced a "change of heart" and that he had been "too enthusiastic" about the use of stem cell therapy.
But panel chairman Professor Brian Gomes da Costa, said: "It [the panel] notes that this is a case in which there is a consistent and potentially unsafe thread running throughout its course.
"Despite your assertions that you have reflected on your failings, the panel is concerned that you have demonstrated little insight into the seriousness of your misconduct and the effects this may have had on your patients.
"It cannot conclude that the misconduct found proved will not be repeated.
"The panel has determined that the totality of the facts found proved constitute repeated and serious breaches of many of the essential tenets of 'Good Medical Practice'."
Besides his clinic in Rotterdam, Trossel had consulting rooms in New Cavendish Street and Wimpole Street, London.
In October 2006, he was ordered by the Dutch authorities to cease stem cell treatment, the GMC heard.
The panel also heard that the doctor's fitness to practise was impaired because of a conviction in Antwerp last year over stem cell treatment offences under Belgian law.
The GMC ruled he had not acted in the best interests of seven patients and an undercover journalist, posing as a Hogkin's disease sufferer, who visited him for the 'pioneering' treatment between 2004 and 2006.
Trossel admitted using stem cells shipped from the United States by a lawyer and an ex-model on the run from the FBI.