A former master of the Coombe Maternity Hospital in Dublin has told the Public Accounts Committee that it will be a "financial and medical catastrophe" if a maternity hospital is not built on the site of the new children's hospital.
Chris Fitzpatrick said that maternity co-location was vital for critically ill babies who have the highest mortality rates.
"If a maternity hospital can never be built on this site, or when the National Children's Hospital is built there is simply no room left for a maternity hospital, then the state will have built the most expensive hospital in the world on the wrong site. This would be a financial and medical catastrophe," he said.
Mr Fitzpatrick added the 200 critically ill babies born every year should not be made to suffer because of poor decision making on the project.
He said there was lack of trust that the maternity co-location would actually happen.
Mr Fitzpatrick called on the committee to recommend accelerating the co-location of a maternity hospital on the St James' Hospital site.
Meanwhile, in an earlier session, chair of the committee Fianna Fáil TD Seán Fleming said he is seeking urgent clarification on whether there was a conflict of interest for consultants PWC in carrying out the cost escalation report on the children's hospital which was published this week.
Mr Fleming said correspondence to the committee from the Department of Health cites PWC as being among the advisors last year when a decision on whether to proceed with or re-tender the hospital had to be made.