New allegations have emerged that the HSE has awarded some contracts to former staff without a tendering process.
The claims are made in a comprehensive dossier sent to the Dáil's Public Accounts Committee.
They are understood to include cases where the HSE has paid former staff members for spaces in care homes, without first investigating whether better deals could be found elsewhere.
Fine Gael TD John Deasy said the claims are worrying, especially given the allegations of abuse in some nursing homes in the past.
"The thought that somebody would be contracted and that they might have a potential conflict is very worrying," he said.
"I think we need to find out the scale of this ... one of the jobs of the committee would be to find out how widespread a practice this is within the HSE."
Committee Chairman John McGuinness said some former staff members have made huge money from unadvertised HSE contracts.
"In once case, at least, a report was prepared, and it cost €98,000 - and then that report was reviewed by another company at a cost of €58,000," he said.
"This is all happening between the HSE and companies outside of the HSE, who happen to employ former employees - of the HSE."