Concerns have been raised that the costs for the new National Children's Hospital are 'out of control'.
Currently, the project has a pricetag of €1.7 billion.
Earlier this week, Taoiseach Leo Varadkar confirmed the contractor building the new hospital has submitted claims for extra costs.
He told the Dáil the claims have yet to be adjudicated.
In an letter to the Public Accounts Committee (PAC) and read out this morning, the National Pediatric Hospital Development Board chief officer David Gunning said: "As reported to the Public Accounts Committee in January 2019 and May 2019, there are a number of exceptions that have been outside the approved Budget for which there cannot be price certainty at this point or for the duration of the project."
PAC chair Sean Fleming suggested there appears to be a "dual system" in place - the approved budget, and a parallel system of exceptions outside that.
He argued: "We have a system, effectively, of double recording - two independent methods of recording the costs.
"They actually say it cannot be priced at this stage or even how long it's going to take - that's an extraordinary admission."
Deputy Fleming said representatives of the board will appear before the PAC in a few weeks, and members will need to "get to the bottom" of the situation.
'Out of control'
Labour TD Alan Kelly argued that the public deserves to know all costs related to the project.
He said: "I remember a significant number of months ago that I said this project would go over €2 billion.
"The Taoiseach in the Dáil said that - he didn't reference me by name - I was exaggerating, or people who were saying this were exaggerating.
"I would now ask the Taoiseach to guarantee that this isn't going to go over €2 billion.
"When [the representatives] are before us in a couple of weeks, chairman, we have to absolutely go through this at a level of detail that hasn't been seen before - because this thing is out of control."
The Social Democrats TD Catherine Murphy, meanwhile, pointed out that the money being spent on the project is 'not Monopoly money'.
She insisted: "We really do have to keep a very, very close eye on this.
"We need to actually have someone come in and talk to us about the cost control side of it at this stage - because unless we keep a grip on that and interrogate the additional bills that are coming in... that's where we're going to run into even bigger cost overruns."