The public spending watchdog is demanding that health chiefs explain procedures for hiring consultants charging up to €1,000 per day in some cases.
The members of the Public Accounts Committee (PAC) have summoned the Health Service Executive to explain the cost and selection of outside consultants hired to carry out investigations.
Some of the investigations involved care standards - including cases of alleged abuse. PAC chairman John McGuinness said he was concerned that former HSE staff are sometimes chosen to do this work.
Documents related to these matters show that several inquiries were commissioned without the competitive tendering process usually required by public service spending rules. The HSE's own rule book says this must happen where former staff are being drafted in to do such contract work.
The documents associated with the case also show some people working on the investigations were paid a fee of almost €1,000 per day.
The PAC is expected to focus on one case about an examination of allegations that a vulnerable person in care was placed at risk. This led to two outside investigations - one costing over €98,000.
Another inquiry, costing €58,000, followed to establish whether there were any similar cases. This was carried out by a consultancy company staffed by some former HSE workers.
The HSE has said it will appear before the PAC next month.