A review into the care of five Wellington mental health patients, each involved in separate homicides, is prompting calls for a national inquiry into the sector.

Capital and Coast, Hutt Valley and Wairarapa District Health Boards have all been put under scrutiny.

The review was ordered last year after a spate of killings by different mental health patients over 15 months in 2015 and 2016, including the killing of Kapiti nurse Cathy Stewart.

Two key recommendations were made.

One was to develop a single electronic record for mental health patients and the second was to have more clarity in client recovery plans.

Some in the health industry have questioned whether better paperwork is enough to address the problems the mental health sector is facing.

Mental Health Foundation of New Zealand chief executive Shaun Robinson said the improvements would go a long way but did not deal with the real issue at hand.

"Some of the staff involved in some of these particular incidents had case loads of over one hundred people," he said.

"It’s just not going to be possible to do the level of work on people’s recovery, and the level of work to ensure the systems are working well for the patient and the community, when you’re that over stretched."

He said the mental health sector desperately needed more staff if meaningful changes were going to be made.

"Simply having lots of records, improved records, is not enough to manage difficult and complex situations."

Green MP Julie Anne Genter said the Wellington review added to the call for a nationwide mental health inquiry.

"DHBs can make improvements to their existing systems but ultimately they’re limited to what they can do if they don’t have enough resources from central government," she said.

Genter said the mental health system was at breaking point and an inquiry was not something that could be put off.

"It’s incredibly important that we look after our people. It’s very very tragic and I certainly feel for all the families affected by incidents like the one that caused the review in Wellington."

Mental Health general manager for all three district health boards involved in the review, Nigel Fairley, said there was a real commitment to implementing the recommendations.

An advisory group, which includes two external mental health clinic experts, has been set up following the review.

"We have been through that process, systematically going through the recommendations and implementing them," Fairley said. 

He said between them, the three district health boards deal with about 16,000 mental health patients annually and more than $140 million was being invested in their mental health care this year.

"I think the important point is we always want to do better. Our service is always committed to providing the best possible care."