The issue of top-ups to high earners in the health sector will come under scrutiny again today when HSE officials appear before the Oireachtas Health Committee.
The health service has been looking into remuneration packages in so-called Section 38 agencies that are funded by the public purse.
It is understood that a number of senior staff at the National Maternity Hospital are earning more than the public service pay cap.
Chairman of the Health Committee, Fine Gael's Jerry Buttimer, said some Section 38 employment contracts permit top-up payments.
"There are certain categories of certain contracts where they can earn private money and also earn from their public practice," he said.
"That exists, and what we must look at is how we want to see a health system evolve in the future."
Fianna Fail's Health Spokesman, Billy Kelleher, called for Section 38 contracts to be made public.
"We can redact very sensitive personal details in terms of the contract, to anonymise it," he said, "but I still believe that people should at least know what type of contracts [were made] - who entered in to them, how they were crafted … and whether they're being adhered to."