Melbourne: A Melbourne doctor under investigation for helping parents evade compulsory vaccinations was reprimanded a decade ago for failing to properly treat patients with potentially life-threatening illnesses like cancer and depression.

The Australian Health Practitioner Regulation Agency (Ahpra) is investigating Dr John Piesse after a video was uncovered of him speaking at an anti-vaccination event in August. In the video, he boasts that he can help parents jump through hoops to get their children exempt from Victoria’s “no jab, no play” legislation and the federal government’s “no jab, no pay” legislation.

The video prompted the federal health minister, Greg Hunt, to say on Thursday that he was “astonished” that someone with a medical degree “would deign to stoop to the level of supporting the anti-vaccination movement”. Victoria’s acting health minister, Martin Foley, said Ahpra’s investigation into Piesse began 12 months ago and that he was concerned it was taking so long, saying it was “not good enough”.

Hunt told Guardian Australia he would be raising the matter of anti-vaccination doctors with state and territory ministers: “It’s dangerous, irresponsible and goes against medical evidence,” he said. “Anyone with concerns about a doctor promoting ‘anti-vaxxer’ practices should contact the authorities.”

By Friday the Medical Board of Australia told Piesse that it intended to revoke his medical registration. Piesse, a supporter of alternative medicine, has a right-of-reply before that occurs, including an opportunity to outline why his licence should not be revoked. The time period usually allowed for a reply is one week.

But a report uncovered by Guardian Australia shows that concerns about Piesse were raised as far back as 2001, when Medicare Australia reported him because he charged Medicare for long and prolonged consultations, and because he made an abnormally high number of pathology requests during the year 2000. He rendered 2,137 services to 707 patients at a total Medicare benefit of $87,570 that year. In July 2003, a professional review committee investigating the allegations found Piesse’s conduct during 2000 “caused a significant threat to the life or health of his patients”.

“It was concerned that Dr Piesse failed to make appropriate investigations of patient symptoms of possibly serious conditions such as cancer, meningitis, depression, and anaemia,” a report from the professional services review scheme said. The committee also found Piesse administered multiple vitamin B doses from one vial.

This information was referred to the Medical Practitioners Board of Victoria, which in August 2004 ordered that Piesse be reprimanded, counselled, repay Medicare benefits totalling $18,179 (Dh66,772), and be disqualified for 18 months from providing certain GP services to patients. In 2007, the Medical Board of Australia ordered Piesse provide a statutory declaration every three months “to confirm that he has not facilitated the administration of intravenous herbal infusions, genome therapies, and other therapies brought into the country by patients, unless the therapies have been specifically approved by the Therapeutic Goods Administration”.

Piesse later admitted that he had failed to provide these statutory declarations, telling the board: “I acknowledge that I did not initially provide statutory declarations ... The reason for the delay in initially providing the statutory declarations was that I was very disturbed by the restriction and implications of this determination in denying safe, beneficial treatment for my patients.” He was ordered to provide the statutory declarations in future and to undertake further education in critical thinking and research. Bill Madden, a medical lawyer and special counsel with law firm Carroll & O’Dea, said in light of the anti-vaccination comments Piesse may face more than just disciplinary action from Ahpra. “It’s always possible that any patients or children could have a right to bring civil civil proceedings against him for financial compensation if his advice has resulted in the suffering of a severe illness,” Madden said.

Guardian Australia has contacted the Victorian health minister, Jill Hennessy, for comment. A statement issued by the Royal Australian College of General Practitioners on Friday afternoon said “anti-vaccination messages have absolutely no place in general practice”. The president of the college, Dr Bastian Seidel, said it was vital all Australians were fully vaccinated. “While some parents may have concerns stemming from reading misleading immunisation information, anti-vaccination messages are dangerous and are not supported [by the college].”