The Victorian government has announced paramedics rather than police will become the first responders to mental health call-outs.
The government says the plan aims to improve health outcomes for patients and free up police to focus on crime.
The Victorian Ambulance Union says it was not consulted about the plan.
The union representing Victoria's ambulance workers says it found out about a plan for paramedics to take over responsibility for mental health call-outs through the media.
The Victorian government has announced new protocols to transition to a health-led response to mental crisis incidents.
Under the plan, paramedics will be the first responders to call-outs whenever possible, with police and protective services officers moving to a support role.
It said the aim was to ensure faster and more effective health care, while freeing up police to focus on crime.
"When someone is experiencing a mental health crisis, they deserve a response that puts their health and wellbeing first while keeping them and the community safe," Health Minister Ingrid Stitt said.
"We're making sure our paramedics, mental health workers and police are in step to deliver a health-led response that is patient centred."
The government said Ambulance Victoria, Victoria Police and the Department of Health had signed off on the protocols.
But Victorian Ambulance Union secretary Danny Hill said he was only hearing about the directive now.
"We haven't been consulted, the workforce hasn't been consulted," Mr Hill told 774 ABC Melbourne.
"I found out more about this through the media.
"They've realised they haven't consulted, and there's a few meetings in the diary, but I know more about this from the media release than I do from them."
Mr Hill said the details he had read sounded like a better outcome for patients but he was concerned about the risks to paramedics.
"We've always supported a health-led response … but for the vast majority of cases, it does need to be a co-response between ambulance and police," he said.
"They're really complicated cases to attend and they're often the cases where our members experience harm, aggression and violence, so freeing up police from those cases is going to be pretty alarming to our members."