The chair of the board overseeing the new National Children's Hospital is warning the project's costs could rise even further.

The Oireachtas Health Committee has heard there ha been no overspend on the budget, since the Government approved the revised bill for the hospital last year.

The building frame of the new National Children's Hospital is now under construction, as controversy continues over its cost.

Excavation works at the St James's Hospital site have been ongoing for the past year, but the frame - which can be seen above ground - along with mechanical and electrical work has started.

The hospital budget is €1.4bn - over €1bn more than what was initially thought - due to an underestimation of how much money was needed to finish it.

But chair of the National Paediatric Hospital Development Board, Fred Barry, told the Oireachtas Health Committee inflation could lead to an increase in the cost.

"That is one area where there's a very, very real risk additional monies will have to be paid.

"It's really outside of the control of any individual - it's whatever happens in construction and the economy over the next few years."

Fine Gael's Bernard Durkan has said people should stop saying there has been an overspend.

"The general public can wake up in the morning, read the newspapers and say 'this is appalling stuff' - [but] there's no overspend at all.

"All the works involved so far are within budget".

The committee also heard 3,700 people will be employed at the hospital once its finished.

Reporting by Shane Beatty