The fees were paid out by John Tierney in just one year and represent only half the costs of establishing the agency, which has so far run up a €100m start-up bill.
Tánaiste Eamon Gilmore said the expenditure would not escape scrutiny.
“It does seem to me to be a high figure and I think Irish Water will have to demonstrate that it represents good value for money and that the expenditure was necessary as part of the setup costs.”
Among the beneficiaries are IBM, Accenture, Ernst and Young, and Oracle — all major players in the IT and financial sectors.
Irish Water said much of the money was for hiring consultants to set up the billing system the agency will use later this year to begin charging 1.8m households for their water — at a possible average rate of €350 a year.
“The majority of this expenditure has been on developing IT business capabilities including the development of billing and customer service systems, financial management, and the asset management systems needed to operate as an effective national utility.”
The agency was forced to explain itself after a bullish Mr Tierney provoked anger by seemingly trying to elicit sympathy for the executives tasked with setting up the organisation.
He said four men had effectively been asked to establish a new utility from nothing in the space of a year. “You’d no buildings, you’d no people, you’d no processes,” he told RTÉ, although local authorities will continue to manage water supplies for the next 12 years.
He also brushed off questions about his past record with consultants when he was Dublin city manager and engaged RPS on an €8.3m contract for services relating to the Poolbeg incinerator which ballooned to €32m before the contract was terminated under pressure from Europe.
Fianna Fáil leader Micheál Martin described the €50m figure as extraordinary.
“This is a scandal waiting to evolve,” he said.
People Before Profit TD Richard Boyd Barrett said the fees were a scandal.
“Now we discover that money households are being forced to fork out in property taxes and will be forced to pay in water charges, are not going to provide local services or to fix our decrepit water infrastructure, but instead will be lining the pockets of consultants and high-paid executives.”
Irish Water said expenditure of the scale to date would not be repeated and added: “These costs are being validated by the Commission for Energy Regulation.”
However, the regulator was also facing anger after revealing it might let Irish Water increase charges to boost revenue if households keep demand lower than expected by conserving supplies.
A spokesman said it had yet to be decided whether there would be correlation between charges and national demand but stressed if that principle was adopted, the opposite would apply and charges could be reduced if demand rose.
“There has been no decision on the kind of charging regime. It’s one of many issues to be worked out.”