And union staff who work in acute inpatient units have vowed to campaign on the issue ahead of the next election, warning the Andrews government that the mental health system will collapse without further investment.

Fairfax Media this week revealed that vulnerable people seeking psychiatric treatment in state-run hospitals were increasingly reporting allegations of sexual assault and violence, mostly by other patients. Some managers are also accused of trying to cover up the extent of the abuse.

The Age has since been inundated with personal stories from patients, staff and other insiders, renewing concerns about an escalating crisis.

Grattan Institute health program director Stephen Duckett??? - who last year completed a damning inquiry into hospital safety - blamed the problems in psychiatric wards on overcrowding, stigmatisation against mental health patients, and a lack of reform.

For too long, he said, "mental health care has been a Cinderella - unloved and neglected".

He took aim particularly at state and federal health ministers for excluding mental health in a recently endorsed set of "Hospital Acquired Conditions", which are used to measure the safety of hospitals in general.

"This is blatant discrimination," Dr Duckett said. "The quality and safety of mental health care is an important national issue in Australia. Yet, inexcusably, the Commonwealth and state health ministers have decided to sweep the safety issues in mental health care under the carpet."

Dr Duckett was appointed by Victoria's Health Minister Jill Hennessy to investigate the public health system after a spate of baby deaths at Bacchus Marsh hospital, so his views carry weight within government.

He is not alone in his concerns - last week the Health and Community Services Union also wrote to state Mental Health Minister Martin Foley to inform him that members were "alarmed at the failure of the government to address the systemic issues in Mental Health".

HACSU assistant state secretary Paul Healey says there are about 350 state-wide vacancies across the system, including shortages at Werribee Mercy Hospital, Goulburn Valley Health, and Forensicare's early intervention de-escalation team.

And with 11 months until next year's election, he said the union was prepared to campaign on the issue ahead of the poll, warning the government: "If they don't invest now, the system will collapse."

The comments come as allegations of assault and violence in inpatient units continue to rise, with claims by some insiders that managers are failing to log information properly, doctoring or downplaying reports, or not immediately notifying police when assaults occur.

Mr Foley admitted "the lines of reporting these incidents need to improve". On the question of resources, he said the government had invested $325 million in mental health, leading to "more beds, more staff and a safer environment for Victorians to work and receive the care they need".

New protocols had also been developed for female-only spaces in mental health units, he said.

"Sexual assault is a serious, unacceptable offence and it has no place in our mental health system or indeed anywhere in Victoria," Mr Foley said. "Whether someone is working or receiving treatment in a mental health service - they deserve to feel safe."