TDs have raised concerns that the cost of the National Children's Hospital could rise to almost €2 billion, after its management board revealed the contractors have made an additional half a billion worth of claims.

David Gunning of the National Paediatric Hospital Development Board told the Dáil's Public Accounts Committee that an additional 906 contractor claims have been made with a value of €446 million.

This is in addition to the €1.43bn cost for the project agreed by the Cabinet in 2019.

He was responding to questions from Fianna Fáil TD Paul McAuliffe, who said the figure could mean this "could bring the project up to the region of €1.9bn".

Sinn Féin's Matt Carthy said it was "crazy" that neither the board nor the Department of Health were willing to disclose an estimated final cost of the project citing commercial sensitivities.

"We began with an initial cost of €800m and we could potentially and very likely exceed €2bn in terms of the overall cost," Mr Carthy said.

The Department of Health's Acting Director of Health Infrastructure, Fiona Prendergast, responded: "At no stage has this department ever considered a figure of €2bn.

"I am not sure where this figure is coming from. There is a range of figures in the public domain that we will not comment on."

She said that given the project is "mid-way through a contract with the main contractor" it is "not appropriate now to consider discussing this in open forum".

Fianna Fáil's Cormac Devlin said it was "extremely regrettable" that the committee was not able to get a handle of what the final costs might be.

"We are here on behalf of the public to establish the costs and potentially the exposure to the public purse, how much this project is going to cost.

"For the witnesses to come here and say they won't estimate that out of fear of litigation is worrying from our perspective and from the public perspective. That is not to take away from the importance of the children's hospital," he said.

Fine Gael TD Jennifer Carroll MacNeill took a different view, saying these claims were being defended on behalf of the State and the approach being taken, in not revealing the final cost, "has meant that there has actually been a lower additional cost than may otherwise have been the case by conceding claims repeatedly".