For the first time, mental disorders have overtaken wounds to become the state's third-leading workplace injury.

The annual number of claims for mental disorders has risen by almost 470 in five years while the annual amount paid out in compensation has soared by 45 per cent to $273 million.

Victoria's two biggest worker compensation categories - musculoskeletal complaints and major sprains and strains - have either fallen or remained steady in claim numbers over the same period along with most other physical injuries.

WorkCover data obtained exclusively by The Age also shows the average individual compensation payout for psychological injuries has ballooned from $73,000 in 2008-09 to almost $90,000 in the past financial year.

Mental health group beyondblue attributes the drastic rise in work-related mental stress claims to reduced stigma, heavier workloads and increasing job insecurity.

But it was also being driven by a heightened recognition of the connection between the workplace and mental health, the group said, with a series of high-profile civil lawsuits ending in six and seven-figure payouts from employers found at fault.

Last month, former teacher Peter Doulis was awarded more than $1.3 million in damages for chronic depression after he was found to have been allocated an unduly heavy workload of a western suburbs school's worst-behaved students.

"Cases like these get people thinking about their own workplace and conditions, and reflecting more objectively about situations they may be tolerating," beyondblue head of workplace policy Nick Arvanitis said.

"People are more willing to speak up."

With an estimated one in five workers taking time off work due to feeling mentally unwell in the past year, industry groups and health advocates have urged employers to treat the mental health of their staff as seriously as physical health and safety.

Australian Chamber of Commerce and Industry chief executive Kate Carnell said rising mental health WorkCover claims were presenting a serious problem for employers to tackle.

"It's not just the higher number of claims, it's the higher cost because stress-related claims last longer ... it's more difficult to get people back into the workplace," she said.

"Businesses have been doing it tough for a long time now, and lots of businesses are working on fewer staff than they once were. It does mean more is being expected from employees, and that's fine as long as people know what is expected and that's clear."

Ms Carnell, also a former beyondblue CEO, said the state's declining rate of physical injuries on the job was a result of businesses getting better at implementing safety policies and programs.

But she said a more proactive approach was needed to foster "mentally healthy" workplaces with a focus on setting clear staff expectations, encouraging people to seek help early when needed, and offering a level of flexibility where possible.

"Employers need to understand the importance of having a proactive approach to mental health otherwise they will end up with very significant workers' compensation claims, and that's in nobody's best interests."

A WorkCover spokesman said the high average cost of mental injury claims was due to longer periods of leave from work.

"Mental injuries are often very complex and can require compensation and medical support over longer periods, often leading to a higher average cost," he said.

"The VWA [Victorian WorkCover Authority] continues to work closely with employers and employees about the need to provide safe workplaces, with focus on preventing both physical and mental injuries."

Victorian WorkCover Authority chief executive Denise Cosgrove said statewide injury claims were at a record low, "which demonstrates the value Victorians place on workplace healthy and safety".

Workplace mental health will be one of the key topics discussed with businesses at seminars held across Victoria this week as part of Health and Safety Week.