The value of housing benefit fraud and error in Northern Ireland increased by £1.2 million last year, a public spending watchdog said.
Considerable efforts are being made by the Housing Executive to address the problem, the comptroller and auditor general Kieran Donnelly acknowledged.
Total housing benefit last year was worth £671 million.
An Audit Office report said: “DSD Standards Assurance Unit has estimated that overpayments of housing benefit expenditure due to fraud and error were £22.3 million (3.4 per cent) compared to £21.1 million (3.2 per cent) in 2013.
“Underpayments due to official error were estimated to be £4.4 million (0.7 per cent) compared to £4.8 million (0.7 per cent) in 2013.
“It is recognised that NIHE continues to dedicate considerable efforts and resources to address this ongoing issue.”
Frauds include subletting for profit, providing false information in a housing application and abandoning the property with no one living there.
The report said: “Tenancy fraud deprives those on housing waiting lists and the homeless of a permanent social home and creates significant additional cost for the taxpayer in providing temporary accommodation and in building additional new social homes.”
The auditor’s opinion on the regularity of financial transactions at the Executive noted “significant levels” of estimated fraud and error in housing benefit expenditure.
The review, Financial Auditing and Reporting: General Report by the Comptroller and Auditor General for Northern Ireland – 2015, found a lack of sufficient audit evidence surrounding the management of heating response maintenance and planned maintenance contracts.
A spokesman for the Housing Executive said: “The Housing Executive has maintained its focus on the prevention and detection of fraud and error within housing benefit. It is disappointing that the estimated level of fraud showed an increase against that reported for the previous year.
“We continue to work closely with the Social Security Agency to ensure best practice procedures are being applied, and in fact over the last year have developed enhanced joint working arrangements with the agency in order to help reduce the levels of housing benefit fraud and error.
“During 2014/15, sanctions were taken by the agency in over 740 cases of social security and/or housing benefit fraud.
“The Housing Executive has recovered over £15 million of overpaid housing benefit.”