A high-ranking police officer has told the Royal Commission into Victoria's Mental Health System that police are increasingly acting as first responders as they attend a growing number of mental health call-outs.

Key points: Victorian police say calls involving a "psychiatric crisis" grew by almost 90 per cent in the four years to 2018

Victorian police say calls involving a "psychiatric crisis" grew by almost 90 per cent in the four years to 2018 Assistant Commissioner Glenn Weir says transporting people with mental health issues shouldn't be a core police duty

Assistant Commissioner Glenn Weir says transporting people with mental health issues shouldn't be a core police duty Police want an increased focus on treating people with mental health problems before they get to crisis stage

Eastern Region Assistant Commissioner Glenn Weir, who has 38 years' experience in the police force, told the inquiry police were attending a mental health incident every 12 minutes.

"The number of incidents that we're attending is increasing incredibly," Assistant Commissioner Weir said.

"It is one of the, if not the, pre-eminent issue facing our service."

The Assistant Commissioner said incidents involving a "psychiatric crisis" increased by almost 90 per cent in the four years to 2018.

The commission also heard 14,000 people were detained by police for treatment under the Mental Health Act in 2016-2017, up by almost 170 per cent in just six years.

"It shouldn't be our core duty to be a transport for people experiencing [poor] mental health," he said.

"We seem to have become the agency of first resort over the years."

Assistant Commissioner Weir said police were spending hours with patients waiting for an assessment in emergency department (ED) waiting rooms.

"It is not unusual for multiple police units to be at one ED with multiple people needing assessment," he said.

"The service delivery impediments for the rest of the community, by us having all our available resources tied up there, is significant."

'Revolving door' of repeat call-outs

Wait times, he said, were not improving.

"I'd like to say it has improved, but I can't," he told the commission.

Assistant Commissioner Weir said it was not unusual for police to be called multiple times over just a few days for the same person.

"We do get frustrated by what seems to be sometimes a revolving door around people who are apprehended, taken, assessed," he said.

"And then three or four days later we're back again."

People experiencing mental health issues can come into contact with police in a variety of ways, including welfare checks, public calls for assistance, ambulance requests for transport and the criminal justice system.

Assistant Commissioner Weir called for an increased focus on treating people before they get to crisis stage and reforming the system to make services more integrated and accessible.

"The first time often that police will have any involvement is when it's reached crisis level," he told the commission.

"So the missing middle, as it's been described, is a significant issue in my view," he said, referring to people with needs that are too complex for basic GP support but not critical enough to warrant emergency care.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 10 seconds 1 m 10 s Royal commission chair Penny Armytage speaks to the ABC's Mary Gearin

Mental health patients waiting days in emergency

Earlier today, the royal commission heard that an influx in mental health patients had left emergency departments struggling to admit them.

The commission heard hospitals were regularly breaching a rule that patients should not stay in the emergency department for more than 24 hours.

Director and Emergency Physician at Footscray Hospital, Dr Ainslie Senz, told the commission it was not unusual for the wait to stretch out to multiple days.

"The longest length of stay we've had in the emergency department for a mental health patient is five days."

She told the commission that during their stays in the emergency department, mental patients could not receive any specialist psychiatric care.

Dr Senz said another concern was patients would often miss out on basics, such as showers or meals.

"We're not really well geared to patients who are staying for a long period of time," she told the commission.