Prime Minister Jacinda Ardern has announced a new mental health facility for those with severe intellectual disability and mental health problems.

Ardern made the announcement at the Rātonga-Rua-O-Porirua Mental Health Campus in Porirua, saying $8.4 million in funding would provide a new six-unit secure facility to provide individualised care for the most high-needs patients.

The move follows publicity over the case of autistic man Ashley Peacock, who has been in a small room at the psychiatric facility at Porirua for almost eight years, and is about to be moved into the community after years of battling by his parents.

"It may be a small number of people who need this service, but at the moment we are not meeting that need," Ardern said.

"These people are sons and daughters, brothers and sisters. They and the staff who care for them deserve fit for purpose facilities that meet existing needs and this investment ensures that."

Peacock is due to be moved into the community soon, where he will live with specialist staff in a purpose-built home managed by provider Community Corrections.

He was moved to the Tawhirimatea unit at Porirua in 2007 and into the 'de-escalation' wing in 2010 because of psychosis and violence issues.

The new units will be built at the Ratonga-Rua-O-Porirua campus by the CCDHB and cater to those with intellectual disabilities or mental health diagnoses who are under the care of Mental Health Addiction and Intellectual Disability Services.

Health Minister David Clark said he expected the inquiry into mental health and addiction services to report back in October and that it would include "robust" recommendations for those suffering mental health issues.

"In the meantime getting this new facility underway will mean better care for a small group of clients and wider benefits across the sector in terms of reduced pressure on existing facilities."

Clark said the units would provide a greater quality of life for those who had previously been in in-patient services for lengthy periods of time.

"This will provide an opportunity for greater rehabilitative gains and the potential for reintegration into the community."

Mental health was one of the main campaign planks in Labour's election campaign. In January, Ardern announced an Inquiry into Mental Health and Addiction by former Health and Disability Commissioner, Professor Ron Paterson.

At the time, Ardern said mental health issues and addiction were often closely linked.

The inquiry was to assess the current strengths and weaknesses of the community response to mental health, and the broader mental health system.

She also spoke about the need to address the suicide rate during the campaign, speaking of the impact a suicide in a friend's family had on the community she grew up in.

Media coverage of the event was almost scuppered after most outlets refused to agree to sign a wide-ranging Capital and Coast District Health Board confidentiality and non-disclosure agreement which threatened legal proceedings, a ban and trespass in the case of any breach.

The CCDHB eventually relented and allowed media in with a verbal undertaking to respect patient privacy.