Comptroller and Auditor General Seamus McCarthy has strongly criticised the leasing of a Dublin property for €300 million over the next 25 years by the Office of Public Works.
The State's financial watchdog said the property at Miesian Plaza, on Baggot Street, was supposed to be occupied in early 2017 but it did not happen until July this year.
The Dáil Public Accounts Committee was told the estimated cost of the delay was €11m.
The C&AG also identified a flaw in the contract, related to a change in measurement standards, which would cost a further €10m.
The OPW business plan, according to the C&AG, has "no economic appraisal" and there was "little evidence of standard business practice" being followed.
OPW Chairman Maurice Buckley told the committee the cost of the delay was "very much regretted".
While he conceded that "proper documentation" had not been recorded, he stood over the approach adopted by OPW Management.
The property is now occupied by staff from the Department of Health because the old headquarters at Hawkins House has "deteriorated".
In response to a question from Sinn Féin's Jonathan O'Brien, Mr Buckley said that negotiations were still ongoing with the landlord about the issue of measurement in the lease.