Three of the worst offenders - the Tax Office, the Health Department and the Veterans' Affairs Department - have consistently topped the public service's absence rates over the past five years.

The median unscheduled leave rate for Australian Public Service agencies in 2011-12 was 11.1 days, the same as the previous year but up from 9.4 days in 2006-07.

Unscheduled leave includes sick, carer's and compensation leave, as well as unauthorised absences.

This year's State of the Service Report noted that, in general, staff in smaller agencies took fewer days off, while those in larger workplaces took more.

The report also found a link between the number of days an employee was absent due to sickness and how engaged they were with their job and their colleagues, though ''this relationship was only minor''.

Among large workplaces (those with 1000 or more staff), those with the highest median unscheduled leave rate were the Tax Office (15.5 days), Health and Agriculture (15.2 each), Veterans' Affairs (15) and Human Services (14.9).

The agencies whose workers took the least days off were Foreign Affairs (8.3), the Bureau of Meteorology (8.6), AusAID (9), Environment (9.3) and the Treasury (9.7).

The Public Service Commission says attending work when genuinely ill raises health and safety concerns for the sick employee and others.

''On the other hand, high rates of absence are costly and impact on individuals, business units and the organisation as a whole,'' it says.

''Excessive absences often coincide with poor performance, high turnover rates and low organisational commitment.''

The State of the Service Report says government agencies tried many strategies to reduce unscheduled leave, including pay incentives and coaching for managers. However, it said methods that worked ''well in one workplace may not work as effectively elsewhere''.

The Veterans' Affairs Department, which has had a particularly high absence rate over the past five years, used its latest wage agreement to cap the number of sick days staff can take without evidence, such as a medical certificate.