The most senior civil servant in charge of public spending has said major State building projects should not be announced based on "guesstimates" of what they will cost.
Secretary General of the Department of Public Expenditure and Reform Robert Watt told the Dáil Public Accounts Committee, that projects will only be signed-off in future when there is certainty about the final figure.
Mr Watt said there is a need to reform how public contracts are awarded.
He said: "People are putting out numbers about the cost of a project without having set out the detailed design, or tested the market.
"It is a guesstimate, it is not certain".
Sinn Féin's Jonathan O'Brien said it was "bizarre" that the Mr Watt’s opening statement did not mention the National Children's Hospital.
Instead, the statement dealt with the issue of public contracts in general, but Mr Watt did reference the hospital in his opening submission to the Finance Committee, which he also appeared before.
The committees are examining the cost overruns at the National Children's Hospital, which has spiralled from €600m to €1.4 billion and counting.
Mr Watt said the first he learned of the overrun was on 9 November 2018.
He said there is no certainty that a different procurement process would have led to a different price for the new hospital.
The committee heard that the two-stage construction process has been used on two projects in Ireland.
The first one was for the Dunkettle Interchange and the second occasion was for the children's hospital.
Mr O'Brien said there is a "determination not to discuss the National Children's Hospital" and that is why Chief Procurement Officer Paul Quinn, is not before the committee.
"You did not want Mr Quinn to appear before the committee because there would be awkward questions asked of him."
Committee Chairman Sean Fleming said today's meeting cannot solely be about the new hospital but must also deal with other projects.
He said that the discussion must align itself with the invitation to the accounting officer of the Department of Public Expenditure and Reform and the oversight of capital projects.
At the start of his statement to the committee, Mr Watt became embroiled in a row over claims he said committee members were "a mob" that needed to be controlled.
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Sinn Féin's David Culliane told the committee it was reported by a "very responsible journalist" that Mr Watt had said, outside of the committee room, that Mr Fleming "needs to control the mob".
Mr Cullinane said such comments would be "deeply, deeply unsatisfactory".
Mr Watt said he apologised if anyone took offence with anything that he said.
He said: "I don't know what I said. If I said anything that offended anybody, apologies for that.
"I don't recall saying it to be honest but if I did say it, it is a colloquial expression. It is not in any way intended to be demeaning to anybody. I don't recollect to be honest."
Later at the finance committee, Fianna Fáil TD Barry Cowen said the body that granted the hospital board a derogation from the standard forms of contract was "sold a pup".
The committee heard that the two-stage process for the contract was granted by the Government's Contracts Committee for Construction (GCC), which is a "consultative forum" made up of construction professionals.
The group, which is part of the Department of Public Expenditure and Reform, considered a request from the Children's Hospital Board for a derogation from the standard form of contract.
Such derogation can be used for complex large projects that have specific requirements and do not naturally fit with the standard 'lump sum' contracts, Mr Watt told the committee.
Previous derogations were granted for remediation works at Haulbowline Island in Cork and works at the GPO for the 2016 Commemorations. They have been granted 12 times since 2011.
Mr Watt said the contracts committee gave a derogation, "but the responsibility still rests with the hospital board. There was detailed discussions around this, it wasn't like it was nodded through".
Mr Cowen said Mr Watt's department had overall responsibility for sanctioning the tendering strategy.
But Mr Watt responded: "The ultimate responsibility here for the procurement strategy rests with the National Children's Hospital and the day-to-day sanctioning authority was the Department of Health. And I don't want to say that in a way which dumps on them."
Mr Cowen said: "I am convinced that the contracts committee was asked for a derogation and it granted it. It has some responsibility or culpability I would have thought. I would like to see who is on this committee.
"In the future maybe there should be more independent assessment sought by those committees rather than relying on the expertise that are there. Because with all due respect to the expertise that was there, it was sold a pup."