Social Protection Minister Joan Burton has warned that Irish Water must not become a "gold-plated operation".
Ms Burton (inset) has piled the pressure on Irish Water bosses as they prepare to be quizzed over the company's massive €50m consultancy bill.
The Labour politician says it is essential that all costs incurred by the semi-state body undergo "strict management" so that the taxpayer gets "value for money".
Her comments come as Jobs Minister Richard Bruton called for more "openness" in relation to how Irish Water is using public funds.
The Cabinet was today due to discuss a series of issues surrounding Irish Water, including the company's controversial decision to spend €50m on consultancy services.
A number of cabinet ministers have defended the company and said they believed Irish Water would justify the spend when they appear in front of the Oireachtas Environment Committee.
However, Ms Burton has warned that the company must control its costs.
"We want to see all costs under strict management so that there is the best value for money for taxpayers.
And what we want is effectively run operations as opposed to gold-plated operations," she told the Irish Independent.
"I think it's for the officials of Irish Water, because it is a start-up, to explain in detail how and where the money has been spent and how cost-effective that spend has been.
"I welcome the fact they agreed to appear so readily and so rapidly before the committee and I look forward to hearing their answers but it is really important, that we're talking about a cost-effective value for money operation, not a gold-plated operation."
Jobs Minister Richard Bruton insisted that there needed to be more "openness" in relation to the use of public funds.
He said the company was "supported by taxpayers' money" and that it was important that all concerns surrounding the use of money were teased out at the committee.
A number of TDs have called for Mr Hogan to appear in front of the Oireachtas committee to explain how much he knew about spending at Irish Water.
However, Mr Varadkar said accountability for expenditure lies with the company itself and chief executive John Tierney.
Meanwhile, chairman of the Oireachtas Environment Committee, Labour TD Michael McCarthy, said today's sitting represented an "important test" for Irish Water.
"Irish Water, or Uisce Eireann, needs to have the full confidence of the public. The company's representatives will be asked for a full breakdown of this €50m, who it went to and for what service. I expect it to be an open debate," he added.