Police plan to start pulling back from every mental health call-out from November, prioritising events where there is an immediate risk to life and safety.
Police Commissioner Andrew Coster said from 1 November, officers would start the transition.
Police had formally notified Health New Zealand and other stakeholders of their intention to fully phase in the changes by September 2025.
"Mental health demand accounted for 11 percent of calls to our Emergency Communications Centre in the year to May 2024," Coster said.
"Police receives one mental health-related call every seven minutes, taking up about half a million hours of Police front-line time per year.
"Of those events, only five percent had a criminal element and 11 percent of calls are coded P1 and are given a priority response."
It was not sustainable and prevented police from keeping other areas of the community safe, Coster said.
"It impacts on our ability to deliver core policing services."
The volume of mental health related calls was also creating "bottlenecks" at the Emergency Communication Centres, which meant they could not always respond quickly to every call.
Police would continue to respond to mental health events with immediate risks to life and safety, he said.
Mental health workforce gaps
Health New Zealand chief executive Margie Apa said the agency and the Health Ministry were working with police to manage the transition "safely".
However, she signalled the ongoing workforce gaps in mental health presented some challenges.
"As health agencies, our interest is in improving access to mental health services for people that need them in a timely way, while ensuring the health and safety needs of our workforce, patients and their whānau continue to be met.
"This is all about getting the balance right."
Ensuring the transition was managed safely for people who needed mental health services, the workforce and the public was a top priority for Health NZ, the Ministry and Police, Apa said.
Health NZ was working with clinical experts, ED representatives, health and safety specialists, security staff and others to put a robust operational plan in place.
"One of the factors we will need to consider as part of our transition planning is our on-going mental health workforce shortages."
The one-year change programme announced today was part of a wider five-year transition plan underway to move to a multi-agency response to 111 calls, with less reliance on a Police-led model.
The plan included a range of initiatives, such as improving the responsiveness of telehealth services and trialling peer support in emergency departments.
'Not criminals' - Minister
Mental Health Minister Matt Doocey said the changes were the first stage of a transition toward a stronger mental health-led response for those in distress.
"This Government is committed to improving mental health outcomes for New Zealanders. For too long, those seeking crisis support have often been met by a uniformed officer, which can cause further distress," he said.
"People in mental distress are not criminals. Those seeking assistance deserve a mental health response, rather than a criminal justice response."
Police Minister Mark Mitchell said the significant increase in mental health demand with police being the default first port of call was "no longer sustainable".
"I want to acknowledge our police staff who do an outstanding job with great empathy, but they are not trained mental health experts.
"Ultimately, we want to ensure people are getting the right care, at the right time, from the right people, and that our front-line officers have more time to focus on core policing and delivering the services expected of them to keep communities safe."
Government 'playing Russian Roulette' - Ingrid Leary
The Labour Party said the change would put lives at risk.
Mental health spokesperson Ingrid Leary said Doocey should demand police stay involved in all 111 call outs "until he can guarantee safety won't be compromised".
"Matt Doocey is playing Russian Roulette by agreeing to roll out a new emergency response system for mental health call outs that doesn't involve police before having all the pieces in place to ensure safety of people and first responders," she said.
"Multiagency response may well prove to be the right direction of travel - however agreeing to jump to a whole new system without police, nor adequate data, enough mental health workers, funding and public education is dangerous and shows the minister is out of his depth."
Four phases
Phase 1: 1 November
At emergency departments - Police will immediately depart after handing over to clinical staff when someone is waiting for a voluntary mental health assessment
Higher threshold for mental health transportation requests
Attendance at mental health facilities subject to a higher threshold
Phase 2: January to March 2025
60 minute ED handovers - Police who have transported a person detained under the Mental Health Act for an assessment will remain for a maximum one hour before departing unless they consider there is an immediate risk to life or safety
Mental Health custody rules tightened - Police do not consider custody suites to be an appropriate place for mental health assessments to be conducted.
Custody rules will ensure people in distress are not being assessed unnecessarily in Police custody.
Phase 3: April to June 2025
Requests for assistance from health practitioners - Our new threshold will ensure Police are not directed unnecessarily to mental health work by practitioners
Missing Mental Health patients - police want a "more appropriate model" for searching for patients missing from mental health facilities and wards, that does not involve Police in the first instance
Phase 4: July to September 2025
15 minute ED handovers - Where police have detained a person under the Mental Health Act and transported them to an ED for mental health assessment, a handover process between Police and Health staff will occur, and Police staff will depart after 15 minutes, unless they consider there is an immediate threat to life or safety
Welfare checks from public and agencies - Police have been over responding to welfare checks where there is no risk of criminality or to life or safety.