The Public Accounts Committee wants immediate clarity over any possible conflict of interest over firm PwC which not only advised health chiefs on the children's hospital, but also completed a review of the project.
The committee heard this morning that PwC was involved in advising over the second phase of the massive children's hospital project last November.
A review by PwC of cost overruns for the €1.7bn project was only released this week after that was separately commissioned by the government.
PAC chairman Sean Fleming said he wants the Department of Health and the HSE to "immediately clarify" why PwC was chosen to do the review, after it previously advised about the second stage of the hospital build.
Its role in the project emerged in a document discussed by members at PAC this morning.
Three options had been considered as part of the second phase of the hospital build.
And a HSE document confirmed that PwC and others had given advice to the HSE, after a request from the Department of Health.
PAC member Marc McSharry also questioned the value of PwC's review now on the hospital cost and whether it was a “waste” as it was now known they advised health chiefs previously on options for the second phase of the hospital.
Both the HSE and Department of Health will be asked today to come back to explain why PwC was chosen for the recent review after previously being involved in the hospital build options.