An internal report for the Office of Public Works found that the agency overpaid by €1.4 million in taxpayer money when buying a property in Fairgreen, Galway city.
The overspend on this property to house the Revenue Commissioners happened because the annual rent was miscalculated, costing an extra €141,000 a year.
The report says that the OPW increased the rent it paid by 13 percent by changing the code of measurement from net to gross internal area.
OPW valuers raised this issue, but the deal went ahead as it was despite their warnings.
This unpublished report was seen by the Irish Times, which said that the state lost €31 million of taxpayers money in five property deals over the course of four years it overpaid in.
The report was completed by two surveyors working for the OPW and sent to Comptroller and Auditor General and to the Oireachtas Public Accounts Committee.
The report concludes that the culture at the OPW was resulting in poor value for taxpayer money.
It also warned of the potential for corruption within the process because the agency tolerates the waste of money within the system.
Of the five transaction analysed in the report, the largest by far was the purchase of Thornton Hall in North Dublin.
It ended up costing €20 million more than an alternative site because of the need to buy additional adjoining land and build an access road.
It was purchased in 2005 for just under €30 million for the construction of a prison, but sits empty to this day.
Other incidents highlighted in the report include a €6 million overspend on buying apartments for demolition in Merrion Square, Dublin to expand the National Gallery.
A site for Department of Education Offices in Mullingar cost €2.9 million more than a less central alternative.
And waiting an extra year meant the OPW overpaid by €750,000 for 14 acres of land near Castletown, Co. Kildare which were finally bought for €2 million in 2006.
The review found that while there was no evidence of corruption in the deals, but the authors said the represented the “tip of the iceberg” in poor spending of taxpayer money.
In a statement the OPW rejected any claims that there was a culture of indifference to taxpayers money in the organisation.
The report recommended that the mechanism for property management should be taken from the Civil Service and given to a commercial state agency similar to the arrangement with Coillte.