The health watchdog said it closed a sexual abuse investigation into a doctor later convicted of molesting teenage boys because there was no public interest in the matter.
A national inquiry has heard of extended delays in investigating a complaint made against former doctor John Rolleston by a man known as AWC, who was sexually abused by the doctor in 1979.
After AWC first complained to the Health Care Complaints Commission in 1998, a report issued three years later said the investigation would be terminated and no action taken in part because "after 22 years there is no longer public interest in taking disciplinary action".
"Significantly," the investigation report said, "Mr AWC could not identify the practitioner and made no complaint to anyone about Dr Rolleston's alleged misconduct until 1998."
Rolleston was eventually found guilty by a court on 30 counts of molesting teenage boys in the 1970s and sentenced to four years jail.
Former Health Care Complaints Commissioner Amanda Adrian told the Royal Commission into Institutional Responses to Child Sexual Abuse she had no memory of the investigation report or AWC's complaint.
"But the argument may have been put that there had been no further conduct of that doctor that we knew of at that time that would warrant - you know, there had been nothing else to come forward," she said.
"I can only speculate."
Ms Adrian said she did not agree with this rationale and said a denial by a doctor should not be a reason for terminating an investigation.
In its 2001 investigative report, the HCCC said it considered referring the matter to the Director of Public Prosecutions and the Department of Community Services but decided not to "for the same reasons it has decided to terminate the matter".
The commission earlier heard there was a 10-month gap between the health watchdog deciding to investigate Rolleston, who was the Director of Medicine at Broken Hill Hospital, and launching the investigation.
Another former HCCC commissioner, Professor Merrilyn Walton, said she was surprised by the delay and it was not routine.
She also apologised to AWC for the delays.
The HCCC eventually reopened AWC's matter and recontacted him in 2007, eight years after he first made the complaint.
It took 20 years to deregister Rolleston even though there were numerous complaints about him in the 1990s.
The commission heard he was briefly deregistered in 1986 following two complaints - one for fraud - and was re-registered in 1990.
Rolleston was not struck off until 2013, two years after he was jailed for historical child sexual abuse.
He was found guilty on 30 counts of molesting teenage boys in the 1970s and sentenced to four years in jail.
He is now on parole and is ill.
