IRISH Water boss John Tierney will face a Dail committee to explain the €100m spend on start-up costs.
At the centre of the quizzing will be questions about the €50m spent on consultant fees.
Mr Tierney made it clear that he would meet as soon as possible with whichever group of TDs and Senators wanted him.
It has emerged that the watchdog Public Accounts Committee (PAC) did not have jurisdiction and a hearing of the Oireachtas Environment Committee scheduled for February was brought forward to Tuesday next.
After a difficult interview with RTE's Sean O'Rourke, Mr Tierney himself returned to the airwaves to argue his case with a second lengthy radio interview.
He told Newstalk Radio that up to €2.2bn would be saved between now and 2021 by more efficient water services but the charges to be paid would not be known until later this year after consultation with the Commission for Energy Regulation.
A spokesman for Irish Water said Mr Tierney would attend any Oireachtas committee, including the PAC if requested.
Eventually, a Dail spokesman said a scheduled hearing of the Oireachtas Environment Committee with senior Irish Water bosses would be brought forward from a date in February to next Tuesday.
Minister for Agriculture Simon Coveny insisted Irish Water must have a chance to explain matters in full.
"People need to put this in perspective. Ireland spends €1.2bn per year providing water to households and businesses," he said.
"That is just 5pc of that."
Environment Minister Phil Hogan said that although the costs were high, they were necessary.
He said Irish Water was taking over responsibility for 34 local councils in charge of water and the overall costs were comparable with what it would take to set up the ESB from scratch.
"These particular costs have been openly tendered for and they have been verified by the regulator. This is going to be a very cost-effective and lean operation," Mr Hogan told KCLR local radio in Kilkenny.
But Fianna Fail said Irish Water had spiralling costs which will mean higher water bills for consumers.
FF environment spokesman Barry Cowen said neither the company nor the Government had provided enough information about its establishment. He said it was deliberately clouded in secrecy and had been exempted from the Freedom of Information Act.
Independent TD Shane Ross and Fine Gael TD Simon Harris said Irish Water should appear before the PAC.
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