Sick leave in the NI Civil Service is costing more than £30m a year, according to a new report.
The average worker misses 12.6 days a year - equivalent to two and a half working weeks.
Anxiety, stress, depression and other psychiatric illnesses accounted for the greatest proportion of days lost.
The sick rate has fallen slightly on the previous year.
The figures emerged in a report published yesterday by the Northern Ireland Statistics and Research Agency.
TUV leader Jim Allister said public sector sick rates were too high, and claimed the system was being abused.
Yesterday's report looks at sickness absence across the Civil Service in the 2018/19 financial year, and recent trends.
Its key findings include:
The report notes the drop in sick leave is the first reduction since 2013/2014.
It states the decrease is mainly due to the spike in flu absences that occurred in the winter of 2017/18 not being repeated in 2018/19.
Mr Allister said the Civil Service sick rate was deeply concerning. "It raises the question - one that has never been answered - as to why those in the public sector are more prone to sickness than those in the private sector, particularly those who are self-employed," he said.
"It is quite clear that there is an element of abuse of sick leave in the public sector. Of course people will be genuinely sick, but it is hard to believe that levels of genuine sickness are at the rate these figures suggest."
Anxiety, stress, depression and other psychiatric illnesses was the absence reason that accounted for the greatest proportion of working days lost (38.7%) during 2018/2019.
Within this category, work-related stress accounted for approximately a third of the days lost.
Alison Millar, the general secretary of the Nipsa union, which represents many public sector workers, said: "There has been an improvement in the figures since last year.
"However, behind every absence is a person - those on long term sick leave need support and assistance to allow them to return to work when they are recovered and we have been working with the NICS to try to ensure the appropriate support and assistance is in place. It is not a one size fits all.
"The positive story is that over half of the staff did not have any sick absence which is an improvement over the previous period. There remains much work to do and Nipsa is committed to work with the NICS to see benefits for all staff, however people do get sick and need supported."
A spokesperson for the Department of Finance said: "Over 51% of staff had no sick absence at all during 2018/19 - the highest proportion of staff without an absence for four years.
"Behind these figures are real people who do not want to be sick or miss work. This is evidenced by the fact that the vast majority (nearly 90%) of working days lost were covered by a medical certificate.
"The sick absence reasons highlighted by the report, particularly in relation to absence due to anxiety, stress, depression and psychiatric illness are unfortunately not unique to the NICS but reflect trends across the wider public and private sectors.
"The Civil Service is proactively delivering a range of health and well-being activities and programmes to help make a positive difference to people's lives."