THE number of sick days taken by Derby City Council non-school staff is expected to average nearly 10 per person for 2013-14.
This would be an increase from 7.6 in the previous 12 months when the authority was including schools staff in its statistics.
The authority says this change, together with redundancies and restructures, means a drop in the number of staff being looked at which is partly behind the forecast increase.
Unison has put it down to the "current climate" at the council causing stress.
But council leader Paul Bayliss said he fully expected the council to have finished 2013-14 with a better sick day record than Nottingham City Council, Leicester City Council and Derbyshire County Council.
He said: "We have a council going through massive change but I always thought the biggest cause of illness was viral infection.
"The issue for me is that we try to manage people's illness well because we need a healthy workforce."
Nicole Berrisford, Derby Unison branch secretary, said: "If there is an increase, it's down to the current climate.
"The authority has just gone through a pay review that's caused a considerable amount of stress.
"In addition to that, there is ongoing restructuring and threats of compulsory redundancies. Teams have got smaller but workloads have remained the same or increased."
The council was yesterday unable to say how many non-school staff posts it has but the figure was 3,230 in November last year.
A recent report, using 2012 figures, from the Chartered Institute of Personnel and Development, says the "national absence average" is 7.6 days.
A report on the subject drawn up by council officers for its resources and governance board says: "The 2013-14 year-end target, excluding schools, is 7.5 days and the year-end forecast at the end of quarter three is projected as significantly exceeding the target at 9.8 days.
"However, this position has improved from quarter two when the year-end forecast was 10.5 days."
It says viral infection is now the most common reason for absence.
And it says that the amount of sick days down to "stress and related symptoms has reduced from 17.22% to 13.47% during the first quarter of 2013-14 compared to the same period from the last financial year".
Mrs Berrisford said: "I would dispute that slightly because of our getting a higher level of people putting in stress claims through the union."
The report says that other factors which could have an impact on the number of sick days include "seasonal variations, level of manager intervention, e.g. awareness of and consistency of policy application, economic climate and organisational change".
No-one from the council was available yesterday to say how much 2013-14 absences could cost in sick pay.
