Department of Health figures have revealed one in ten public hospital consultants are treating more private patients than their contracts permit.
Specialist doctors may treat between two and three private patients in every ten they see, depending on their contract.
The HSE says a shortage of private facilities in key areas of practice, such as maternity care and transplant, accounted for the figures.
However, Labour Spokesman on Health Alan Kelly says he disagrees with the official interpretation.
"I don't buy the interpretation. I think there is a minority of consultants, and I wouldn't like to paint them all with the one brush, that were shown to be effectively using the public system for their own private practice to a level which is absolutely and totally unacceptable and being subsidised by the taxpayer," he said.
"So we have a long way to go to ensure that that is not going to happen again."