Former Environment Minister Phil Hogan last night rejected claims that he approved payments of more than €40 million to consultants employed by Irish Water.
Ireland's EU Commissioner designate said he approved an overall figure required to establish Irish Water but did not know how much went on consultants.
These included hardware and software systems and a billing system, all of which were absolutely necessary for the state company to get off the ground.
"There was a robust examination of all the costs associated with the establishment of Irish Water by New Era and the National Development Finance Agency. The figures were then verified by the regulator and I ultimately approved them. All of the costs were approved and independently verified as necessary for the establishment of the new company," Mr Hogan said.
But according to the opposition, Mr Hogan is "not the right person" to be Ireland's next European Commissioner.
RTE's This Week programme said Mr Hogan knew of, as far back as December 2012, funds totalling more than €40m to cover the cost of external consultants working for Irish Water. Mr Hogan signed and approved of the document on 10 December 2012.
Reform Alliance TD and former Fine Gael minister Lucinda Creighton said Mr Hogan's claims of ignorance "don't stack up".
Sinn Fein's deputy leader Mary Lou McDonald said that Mr Hogan was not the right person to be Ireland's voice in Europe.
"He should come forward an offer a more fulsome explanation. It is important that you have a steady transparent and absolutely credible person and frankly I don't believe that Phil Hogan is that person," she added.