The Public Accounts Committee will be calling the management team of Irish Water up to explain €50m spent on consultancy fees, TD Simon Harris said.
The head of Irish Water, John Tierney, claims the consultancy services that cost €50m sought by the company were value for money.
The body now responsible for the supply of water says the spending of such money was necessary in the set-up of a new utility service - costs which will have to be recouped by the company.
The company says as yet there has been no decision made on what charges people are likely to face, but they have warned that those who do not pay their water charges will face a disruption to their service.
Mr Tierney has not ruled out further costs in the set-up of the water charging scheme.
He said: "The spend on consultancy is part of the set-up cost.
"There is very little spend on consultancy as part of the enduring organisation, except where in the capital programme you would obviously hire consultancies as part of the design and construction scheme."
Minister for the Environment, Phil Hogan, defended the move as a necessary one.
"Governance issues legal issues, setting up IT systems, setting up service level agreements … a customer building system, an new HR department - these are all essential parts of setting up a semi-state company," he said.
Tánaiste Eamon Gilmore has also said he expects the expenditure to fully explained.
Fianna Fáil, meanwhile, said it will introduce a motion to the Dáil demanding transparency, saying Irish Water is a "runaway train" with no accountability.