Officials were praised for saving £17.3m since 2012, through imposing new standards on working space and changing rules on leasing properties.
But these savings were cancelled out by the fact that more than 6,000 desks for civil servants sat empty – 18% of the total work stations available – at an estimated cost to the taxpayer of £17.7m.
The civil service is still working on an estate which consists of “highly inefficient, cellular and ageing accommodation,” said Kieran Donnelly, Northern Ireland's comptroller and auditor general.
There are no formal targets for saving money against the office estate, which comprises 276 offices with direct running costs estimated at £96m a year.
Donnelly also criticised the slow implementation of recommendations made since his last report and argued long-term future savings were unlikely without prompt investment in more modern working space for staff.
The report asked officials to “attach a higher priority” to gathering data on how efficiently buildings across the estate were used.
It also suggested creating a central register of “surplus assets” so that government-owned buildings rarely or never used could be considered for sale.
The NI Audit Office explained progress had been made on publishing the first region-wide strategy on managing the estate, as well the use of 'Invest to Save' funding, which is hoped to generate annual savings of £5m in years to come.
Donnelly said. “I welcome the generation of £17.7m in savings across the office estate since the 202 report but many opportunities still exist to release further, significant savings”.
He added: “It is important that the required upfront funding is now invested to facilitate the procurement, or refurbishment of existing, buildings to accommodate higher numbers and densities of staff in modern, space efficient and fit for purpose premises.
“Without such investment, the predicted release of savings is unlikely to be achieved”.
He also looked forward to the roll-out of a new scheme from the Department of Finance, the Reform of Property Management programme, which will centralise the management of the office estate and, he hoped, “address many of the longstanding problems”.
