Canterbury's DHB says its working to address a startling number of assaults on Christchurch Hospital's ED staff

Research in the New Zealand Medical Journal shows violence at the city's hospital's emergency department is worse than ever and going under-reported.

An annual audit every May in the past seven years, indicates higher levels of violence towards staff is reported in comparison to other parts of the year.

CEO Peter Bramley says no level of violence is acceptable in any workplace, and it's working on a structured programme.

The work includes improving de-escalation techniques, updating security technology and emergency response plans.