The territory's 20,000 public servants lodged mental health claims at rates far above their Commonwealth peers last financial year, easily exceeding similar claims by employees in the private sector.

Evidence to Senate Estimate hearings by the workplace insurer Comcare this week showed ACT government bureaucrats recorded 3.6 mental health claims per 1000 workers in 2013-14, surpassing the 1.9 claims per 1000 workers from the Australian Public Service.

Private sector workers lodged just 0.4 claims per 1000 in the same period.

The figures prompted calls for explanation from the ACT Liberal Opposition and come just days after Chief Minister Katy Gallagher said bullying would not be tolerated in territory public service ranks.

More than 6000 employees were surveyed as part of the annual State of the Service report, which found about one fifth had experienced bullying in the workplace.

Between 10 and 20 per cent of survey participants said they had first hand experience of workplace bullying in the time period.

Ms Gallagher referred questions about mental health claims to ACT Public Service Commissioner Bronwen Overton-Clarke on Friday.

Ms Overton-Clarke said the number of workers' compensation claims made in relation to mental health conditions has decreased in the past two financial years and accepted claims in 2013-14 were 1.86 per 1000 workers.

She said the ACT public service workforce was significantly different from other sectors because it combined administration of governance with a large number of frontline service delivery functions including nurses, teachers, corrections officers, firefighters, paramedics and disability support workers.

These relatively high risk occupations delivered higher rates of mental health claims.

"As part of its work health and safety framework, the ACTPS is continually working on decreasing the rates of physical and psychological injuries sustained by workers," Ms Overton-Clarke said.

"Any case of mental health that is a result of a person's employment is of concern to the government and this is why we continue to work closely with staff to address problems at the source and to create a safe and healthy workplace for all employees.

"The ACT Government encourages anyone who feels that they are suffering a mental illness as a result of their employment to come forward and to seek assistance as part of these established programs."

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Ms Gallagher on Thursday described workplace bullying as unacceptable. Facing criticism of the ACT public service's internal culture, she told the ACT Legislative Assembly that new legislation would soon strengthen internal conduct.

Liberal mental health spokeswoman Giulia Jones said the rate of mental health problems reported by public servants was disappointing.

"The Chief Minister needs to find out why the rate is so high and put processes in place to dramatically reduce the suffering of ACT public service employees," she said.

"There needs to be effective and compassionate people management. We know there is a significant amount of bullying on the back of a recent ACTPS survey showing up to 30 percent have witnessed bullying."

Mrs Jones said she expected "a proper response" from Ms Gallagher.

"These are not just statistics, these are our neighbours and our friends who are suffering. It's obvious the government needs to change its attitude towards its employees."

An employee assistance program offers public servants and their family members access to free counselling and a current service improvement plan is in place to promote early intervention and identification of potential psycho-social issues.

Ms Overton-Clarke said a whole of government health and wellbeing policy was in place, as well as tools to manage occupational violence.

The State of the Service report, released in September, found more work was needed to help allay "perceptions and realities of bullying" although the findings were described as similar to levels found in the Victorian public service.

Data in the report showed 160 reports of bullying had been received in 2012, falling to 124 in 2013 and to 96 to date in September.