The Department of Health has said the spiralling cost of the new National Children's Hospital is "disturbing".

Officials from the Department and the HSE are today being grilled on the level of oversight they've had on the project, as the bill for the development continues to increase.

The estimated cost has risen from an original estimate of €650 million to the latest estimate of between €1.4 billion and €1.7 billion.

The Government has warned it will undoubtedly impact other priority health investments.

The Taoiseach told the Dáil no projects will be cancelled to meet the extra cost of building the hospital, but admitted some may have to be delayed while the Department of Health finds the extra money.

Speaking before the Health Committee today, Colm Desmond - Assistant Secretary at the Department of Health - explained that an extra €100 million needs to be found for the hospital this year alone.

He observed: "To complete the build of the hospital and outpatients and urgent care centres, an additional €450 million would need to be found over the period 2019 to 2022.

"The total of €450 million requires net additional exchequer funding of €320 million - of which €50 million is VAT - and an additional €130 million in philanthropy funding. This is a very significant and disturbing escalation in cost."

Earlier, Health Committee chairman Michael Harty said he believes the Department of Public Expenditure and Reform (DPER) should also appear before the committee.

He observed: "I think there are serious questions to be answered on how this project has spiralled out of control.

"We did invite [the DPER] to come in, but unfortunately they have declined to come in - saying that it's not their responsibility... that it is the responsibility of the Department of Health to explain these overruns. We as a committee don't accept that."

The new National Children's Hospital is being built on the campus of St James's Hospital in Dublin, with the facility expected to open in 2022.