Secretary general of the Department of Finance Tom Considine has defended the fact that State projects often cost significantly more than original estimates.
Mr Considine told the Oireachtas Committee on Finance yesterday it was "a bit unrealistic" to expect that initial estimates on projects were maintained.
He said these estimates were often made before detailed design and costings were carried out, and before the addition of inflation costs on the projects, which often take years to complete.
He drew the comparison with a house extension, where he said the final cost almost always exceeds the original estimate.
"There is an onus on everybody to recognise the reality. I am not saying we shouldn't seek to get accurate estimates, but we have to recognise that real issues have to be addressed."
He was making his comments in the wake of reports from the Comptroller and Auditor General and Public Accounts Committee which have highlighted serious cost overruns on State projects, including roads, flood works and computer systems.
Some projects, such as the Kilkenny flood relief scheme, cost five times the original estimate of €10 million.