The Public Accounts Committee will ask the head of the Department of Public Expenditure as well as one of its top officials to answer questions about the spiralling costs for the national children's hospital.
PAC chairman, Sean Fleming, said the committee will frame questions for department secretary general Robert Watt in a general way about spending so he will be required to appear before TDs.
Mr Watt has already declined to appear before the Oireachtas Health Committee on the scandal.
Labour TD Alan Kelly said it is “absolutely necessary” that Mr Watt appears and answer questions.
A €450m overrun in the hospital build, now expected to reach potentially €1.7bn, has triggered significant criticism from the Opposition.
Mr Kelly said a most "unbelievable" aspect of the controversy is that officials from the Department of Public Expenditure tried to sit down with their counterparts in the Department of Health in September last year over the issue, but could not.
It was not until November 9 that Public Expenditure Minister Paschal Donohoe and Taoiseach Leo Varadkar, were informed - after the October Budget and spending negotiations for the year. This was all going on, added Mr Kelly, amid the controversy about other massive overspends in health.
The Labour TD added that ministers and the Taoiseach, in the end, were aware of the concerns and Health had been trying to sit down and talk with public expenditure and they could not.
The PAC also wants the department's chief procurement officer, Paul Quinn, to appear and answer questions on the same matter.
Mr Fleming said it is “totally unsatisfactory” that the committee has already written to Mr Quinn on the same issue, but he had failed to point out that he was on a board overseeing the hospital for the last number if years.
PAC would express "grave disappointment” that that information was not relayed by Mr Quinn to the committee. Nonetheless, Mr Quinn, the committee heard, has already indicated he is available to help PAC with its work.
The committee is also seeking legal advice on the new revised PwC terms for a review into the €1.4bn hospital spend.
TD Catherine Murphy asked whether the probe will identify people or whether it will just be the Government which will know who was involved when the report is completed. The Social Democrats leader explained: “We are not looking for a head, but a lesson on a system of accountability.”
The committee is also to consider a request by Prof Chris Fitzpatrick, the former Master of the Coombe maternity hospital, to outline his concerns over the hospital debacle.
Prof Fitzpatrick wrote to the committee and said he has had “serious concerns about the complexity and costs of developing” on the current site at St James’ Hospital.
Prof Fitzpatrick told the committee that he strongly believes that a formal risk assessment must be now undertaken, as a “matter of urgency”, in relation to the sustainability of the project. The PAC will now consider whether he and others are called for a general hearing about the children's hospital and spending on the project.