The Dáil spending watchdog has been told that spending on the new National Children's Hospital has already exceeded €1 billion - nearly three quarters of its current budget.

In correspondence to the Public Accounts Committee, the Department of Health has confirmed that €1,049,001,707 has been spent so far out of the approved budget of €1.4 billion.

PAC chair Brian Stanley told a meeting of the committee today that the information was concerning because it is already far above the original budget of €800 million, with several years yet to go before completion.

"It exceeds the original estimate for costs and we are still somewhat away from opening the doors of it," Mr Stanley said.

"There are potentially another three years to go in this project."

The committee has previously heard that the contractors, Bam, have made an additional half a billion euro worth of claims which are being contested.

The note to PAC was supplied by Robert Watt, the Secretary General of the Department of Health.

Mr Watt warned that Brexit, the pandemic and recent geopolitical developments have severely impacted construction industry supply chains and more general economic challenges.

He said definitive updates on costs cannot be provided due to the fact that we are talking about a live contract and speculation on any costs will be detrimental to the Development Board's commercial engagements.