Health authorities are examining whether the Croydon Day Surgery should have been told about his conviction, and that he had been deregistered for more than a year in the 1990s.
Dr James Latham Peters worked at the surgery as an anaesthetist since 2006. He allegedly infected patients with his own strain of hepatitis C.
More than 1140 patients to whom he administered anaesthetic have contacted the Health Department and had tests to see if they have contracted the disease. Dozens of patients treated by the anaesthetist have received test results showing they are not infected.
Sources say the Croydon Day Surgery did not know about his previous conviction. His employers had only been told that he had a personal issue around the abuse of intravenous drugs, but the Medical Board had Dr Peters listed as registered to practice.
In 1996 the Melbourne Magistrates Court was told that more than 100 prescriptions for painkillers were written in Dr Peters' wife's maiden name and false names. Dr Peters was found guilty on 20 charges, including obtaining pethidine by false representation and prescribing a drug for purposes other than treatment.
His wife Julia Peters was found guilty on 41 charges. Dr Peters was sentenced to six months in prison and his wife to three months. Both terms were suspended for 18 months. The court was told the drugs were used by Julia Peters.
Before he was convicted in 1996, Dr Peters had voluntarily surrendered his registration. The following year he was granted restricted medical registration by the board.
One woman given an anaesthetic by Dr Peters in August last year says staff at the Croydon clinic were ''fairly unprofessional from start to finish … just the way we were treated''.
''Andrea'' told The Age she had asked Dr Peters for a mild anaesthetic so she would be awake throughout the procedure.
She claims Dr Peters said to her: ''Most women going through what you're going through don't want to remember any of it.''
Despite telling Dr Peters that she wished to remain awake because ''she didn't trust these guys'', she says the dose administered did put her to sleep and she woke up after the termination. She told ABC radio she had since tested negative for hepatitis C.
The department and police are trying to determine how the patients at Croydon Day Surgery were infected. On Friday Victoria's chief health officer, Dr John Carnie, said he referred the matter to police in March because he found it hard to imagine how the transmission of the virus had been accidental.
It is understood that there would have been no need for Dr Peters to reuse needles. There are strict procedures for infection control, but the number of needles used is not correlated with the number of procedures.
The Medical Board will not comment on Dr Peters' issues with drug abuse. Its 2009 annual report shows that 22 doctors were involved in the board's drug abuse program. The board assesses whether such doctors should be permitted to practise and whether there should be any limitations on their duties.
About 70 per cent of people infected with hepatitis C may develop a chronic form of the virus. Of these people, about one-fifth will develop cirrhosis - scarring of the liver that can lead to liver cancer.
Concerned patients can call the Department of Health on 1300 365 677.