Health New Zealand admits nurses working in mental health and addiction are under pressure - but says only a minority of cases involve violence.
According to a survey by the Nurses Organisation released on Wednesday, 76 percent of mental health nurses have been physically threatened and over 40 percent assaulted within a 12 month period.
Increasing violence against staff and patients was symptomatic of wider pressure on the system, especially roster gaps and unsustainable workloads, the union said.
Te Whatu Ora chief people officer Andrew Slater said the agency acknowledged these nurses were working "in a challenging environment".
"Shortages in specialities such as mental health and addiction are a long-standing issue and not unique to New Zealand, with many comparable countries struggling with similar challenges.
"We have a broad programme of work underway both to grow and upskill existing mental health and addiction workforces, while also developing new workforces to better support people's mental health and addiction needs."
Mental health was "a challenging and confronting area of nursing", however people had a right to a workplace in which they felt safe, he said.
"It's important to acknowledge the vast majority of interactions our staff have with patients and their whānau are kind and respectful. It's only a minority of cases where our staff may experience aggression of some kind."
All staff were trained in de-escalation techniques and practices.