The cost of sick leave in the Northern Ireland Civil Service is now running at close to £40m a year, a report reveals today.
Absence levels are almost double those recorded in England, auditors found.
Northern Ireland is the only UK region where rates of illness in the civil service have increased significantly over the last five years.
Local councils experience even higher levels of sickness - almost 14 days per employee on average. Again, these are the highest in the UK, with no indication of significant improvement.
The findings are set out in a report published today by the Northern Ireland Audit Office.
It states a concerted effort is required to tackle the issue.
Comptroller and Auditor General Kieran Donnelly said: "High levels of sickness absence within the public sector are not a new phenomenon. However, this report finds few signs of sustained improvement."
The report comes a week after the Audit Office raised concerns over the cost of agency staff to cover workforce gaps in the civil service.
Today's report examines the extent of absence in the civil service and local government, and the reasons for it. It notes the problem has increased since the last report by auditors in 2013, which analysed statistics from the 2010/11 year.
Auditors noted that sick leave rates in Northern Ireland are well ahead of other UK regions and the Irish Republic.
In 2017/18 - the most recent year for which statistics for all regions are available - civil servants here missed 13 days on average.
That is higher than their counterparts in the Republic (10.1 days), the Welsh government (8 days), Scottish government (7.6 days) and England (6.9 days).
One in eight civil servants here had a long-term sickness absence in 2019/20 - 63 days on average.
Long-term absences accounted for over three quarters of all working days lost - equivalent to losing 951 full time staff for an entire year. However, auditors noted that half of NICS staff had no recorded spells of absence.
Today's report, citing analysis from Nisra, notes that mental health issues are a significant and growing cause of absence.
Over 102,000 working days were lost due to anxiety, stress and depression in 2019/20 - almost a third of them attributed to work-related stress.
The report also examines absenteeism across our 11 local councils.
Almost 14 days were lost per employee in local councils in 2018/19 - an increase of 13% since 2014/15. This is also higher than other UK regions.
The report identifies a wide disparity in sick rates at Northern Ireland councils.
At Causeway Coast and Glens the average staff member missed 17.1 days - the highest of all 11 local authorities.
The second highest was at Armagh, Banbridge and Craigavon (16.7 days), with the lowest at Fermanagh and Omagh (10.4 days).
The overall sickness rate at councils has decreased from a high of 15 days in 2016/17, and six of the 11 councils reduced their level of absence by more than 10% year on year.
Mr Donnelly added: "It is time for public sector organisations to make a concerted effort to reduce the level of sickness absence and to develop a consistent approach to managing attendance.
"With that in mind, the Local Government Auditor (Pamela McCreedy) and I identified a number of key principles in managing attendance that should be applied across central and local government.
"A strong attendance culture needs to be embedded across the Northern Ireland public sector, and driven from the top.
"We are recommending that organisations focus on targeting long-term absence through preventative measures and early intervention.
"It is also vital for all organisations to measure and analyse sickness absence levels if they are to understand their impact, not only in terms of cost, but also on the quality of services delivered to the public."
A spokesperson for the Department of Finance said: "The level of sickness absence is regrettable.
"Reducing sick absence rates remains a priority for the Civil Service. The NICS remains committed to working jointly with trade union colleagues and other partners such as our Employee Counselling, Welfare and Occupational Health teams to support colleagues to stay in work and return to work as soon as they are able."