TDs claim there was a “gross conflict of interest” in PwC twice advising on the children's hospital build and say the financial firm was "paid twice for the same job".
Public Accounts Committee members blasted the use of the firm to advise health chiefs about the build and then to later assess problems over escalating costs for the project.
PAC chairman, Sean Fleming, said HSE officials and those from the Department of Health will now be hauled in for questioning to get to the bottom of the matter.
Responding to the claim, PwC said: "We are satisfied that we do not have a conflict of interest."
PwC had advised health authorities last November on the second phase of the hospital construction and helped assess whether a new contractor be hired or that the builders BAM be still retained.
However, following uproar over a dramatic increase in the project costs - now estimated to be €1.7bn - the Government this year ordered a review of the bill for the hospital build.
PwC were hired at a cost of almost half a million euro to do this.
But in recent correspondence to PAC, it emerges they had a dual role, which included the earlier advice to health authorities.
Mr Fleming insisted there was a “gross conflict of interest” and that PwC were retained twice over just a few months. The firm was “paid twice for the same job” argues the chairman.
Sinn Féin's David Cullinane also agreed there is a “breathtaking conflict of interest” to be investigated. He also wants the HSE to breakdown exactly what PwC was paid and wants to know if the same individuals were retained for both jobs.
Independent TD Catherine Connolly said she wants to know if the Government were aware PwC had done the earlier work on the hospital before it was retained for the more recent cost review.
Social Democrat co-leader Catherine Murphy also agrees there was a “conflict of interest” and that it seems there was a “double payment” to PwC for the same work essentially.
If there is a conflict of interest, this causes “corruption of a process” argues the PAC member.
HSE chiefs wrote to the committee in recent days denying that there had been a conflict of interest for PwC in its role advising over the build stages as well as the cost escalation for the project.