Police have admitted they could have done more to help a woman before her son stabbed her.

An Independent Police Conduct Authority report found police underestimated the woman's situation from her first two 111 calls and failed to send officers.

She was then stabbed in the back by her son, who was later found to be insane.

Police communications centre national manager Superintendent Dave Trappitt said they should have acted with greater urgency and not delayed their response.

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"We also share the IPCA's view that if police had attended the address sooner, the stabbing may have been avoided," he said.

"Police have sincerely apologised to the victim for the way in which we responded to her calls."

The woman, from Omapere, Northland, called the police about 6am on October 26, 2015, concerned for the safety of her and her family.

She was concerned because her son, who had mental health issues, was behaving erratically and had pushed her.

Police put the event "on hold" until an existing mental health crisis team appointment took place at 10am.

At 10.43am the woman called 111 for the second time to report the crisis team would not take her son away because they did not consider him to be sick enough. She told police she feared for her safety and did not want her son to stay in the house.

Two officers in Omapere agreed to attend after they had completed an unrelated matter.

At 11.15am, as the officers were about to contact the woman, a third 111 call was made, reporting the woman had been stabbed in the back by her son.

A unit attended immediately.

The injured woman was flown to hospital, and recovered from her wounds.

The authority said police should have gone to the woman after the first 111 call, because of her concerns for her and her family's safety.

The dispatcher should have passed on all of the relevant information from the 111 call to the field supervisor before they decided it was unnecessary to send the on-call officer.

Police also should not have closed the event without telling her they would not attend.

Trappitt said he accepted the report's findings and had learned valuable lessons.

Police have taken several steps, including a review of the event in terms of policy practice and procedures, he said.

Two years ago, in recognition of the 90 mental health-related events policy attend every day, the force modernised its training of recruits, which focuses on giving them a fuller understanding of the needs of mental health service users.

New training that focuses on increasing awareness of mental health and helping people suffering mental distress has also been rolled out to frontline police, including communication centre staff.

Communication centres have also reviewed and updated their standard operating practices requiring constant risk assessment of events under action.

A District Court judge later found that the man was legally insane when the stabbing happened. He was detained under the Mental Health Act.