About half of all mental health-related callouts in the past year were not attended by police, as they were called out to other higher priority situations.
Police's 2020/21 annual report warns that un-met demand for mental health callouts is likely to increase.
The report states police attended more than 70,000 events in that period which involved a person having a mental health crisis or threatening or attempting suicide, a 10 percent increase on the previous year.
"As a result, around half of all mental health call outs were cancelled by Police Communications Centres without us attending them due to even higher priority emergency events."
"Mental health-related events have also increased by 60 percent over the past five years and are predicted to increase by a further 44 percent by 2025."
National's police spokesperson Simeon Brown says it shows an incredibly stretched police force.
"This is putting New Zealanders' lives at significant risk."
Police Minister Poto Williams says the figures are concerning but it's not the police's job to deal with mental health concerns.
"What is at play here is the fact we don't have sufficient crisis intervention services and police are called in as back-stop. They are not trained mental health workers."
Domestic violence callouts have increased at the same rate and the report predicts they will increase 35 percent by 2025.
In the period covered by the report, there were more than 155,000 family harm incidences. The report notes most family harm incidents are not reported.
"Police encourages the reporting of family harm - yet the risk from currently under-reported events on police resources in the future is potentially significant."
Police, at the same time, noticed an "increased level of sophistication and hardening of the criminal mindset particularly across serious offenders and organised crime groups".
"We continue to refine our approach and increase our resourcing in this area to reduce the addiction, distress, dishonesty, and violence that it drives."
In 2017, the coalition government pledged to boost police numbers by 1800 in three years. The report said police were on track to recruit 1800 new officers by 2023.
"However, demand for policing services continues to require us to prioritise our focus across existing and emerging areas of demand."
Brown said the government needed to urgently complete that rollout.
"Not only for making sure they can respond to these mental health callouts, but also the promised cops to support the work around organised crime and gangs."