Trauma from workplace bullying or violence now make up the largest proportion of mental-stress compensation claims among public servants, according to the latest data from federal workplace insurer Comcare.

Mental-stress workers' compensation claims are now costing $342,000 each on average, but there have been nearly 500 mental-stress claims by public servants over the past five years that have cost taxpayers $500,000 or more.

Mental-harm claims have soared by more than 88 per cent since 2009, according to Comcare's latest statistical snapshot.

Nearly 39 per cent of claimants in 2013-2014 said bullying or harassment by their colleagues had left them unable to work, the same proportion of public servants who cited workplace stress as the cause of their psychological problems.

Another 8 per cent of mental-stress claimants said they had been traumatised by "exposure to workplace or occupational violence", with 40 such claims accepted in the 2013-2014 financial year.

The 233 claims linked to bullying or violence accepted by Comcare in 2013-2014 will cost the taxpayer more than $79 million on present trends.

The figure represents just under 20 per cent of the total $410 million spent on claims across the Comcare scheme that year.

The statistics underline the impetus behind efforts across the Australian Public Service and the broader public sector in recent years to combat bullying and perceptions of bullying.

With premium bills to cash-strapped government departments increasing by 20 per cent in 2013-2014, their bosses are on notice that poor performance in preventing workplace injuries and getting public servants back to work will hit their bottom lines.

Since 2009, 2173 mental-stress claims have been accepted from government agency employees, with 475, or 22 per cent, costing more than $500,000 each.

By contrast, only 3.5 per cent of claims for body stressing, which remains the leading cause of public service compensation claims, cost more than $500,000, although Comcare planners are worried by the growing cost of body-stressing claims, which topped an average of $129,000 in 2013-2014.

The insurer has launched a campaign to get public servants out of their seats more often, targeting "sedentary" workplace behaviour, which it says leads to higher rates of chronic disease and injury.

Workers in the public sector, including drivers, call-centre staff or data-entry employees are considered particularly vulnerable to the dangers of prolonged sitting.

The Stand Up Comcare campaign has produced, fact sheets and guides for managers and team leaders on strategies to get their public servants out of their seats, with posters distributed to government workplaces, warning workers of the dangers of sitting down for too long.

"Comcare actively promotes strategies to reduce sedentary behaviour in workplaces and encourages the use of sit-to-stand workstations. We use this type of workstation in our own office locations," a spokesman for the insurer told Fairfax.

"Comcare has conducted successful campaigns and seminars to promote research on the benefits of alternating sitting and standing in the work environment.

"Prolonged sitting is a risk that employers should consider in their work health and safety policies and practices."