Inadequate facilities for people with high mental health needs have been highlighted by the Chief Ombudsman, who says the issue needs to be addressed.
In his annual report, Judge Peter Boshier said the Ombusdman's responsibilities include inspecting prisons and mental health facilities to ensure against cruel and inhumane treatment.
In the past year staff have visited 22 mental health units and prisons, making 198 recommendations, 143 which were accepted or partially accepted.
Of the 24 recommendations not accepted, the majority related to the use of cameras and prisoners' rights to privacy, a lack of privacy screens around toilets, prisoner meal times and insufficient dental care.
Judge Boshier said his office found areas of good practice, but has singled out secure mental health units in Wellington, the Hutt Valley and Taranaki as being unfit for purpose.
He noted those held in privately run dementia units were not subject to the same independent oversight as publicly run units.
The report also referred to the number of prisoner assaults.
A survey of five of the country's prisons found the number of prisoners advising they had been assaulted was high, particularly in the Manawatu and Invercargill prisons, where they accounted for just under half of the respondents.
But it found the number of unreported assaults was even greater.
It said written and oral feedback from prisoners suggested they had little confidence in the complaints system and recommended that prisons in Otago, Invercargill and Manawatu carry out a survey to identify where prisoners felt the least safe.
The report criticised the remand conditions at Invercargill and Manawatu prisons, saying they were unacceptable, where most prisoners were doubled bunked.
"We observed run-down accommodation and a lack of staff supervision, particularly at Invercargill prison, and a culture of intimidation amongst prisoners, especially in the remand exercise yard.
"There was a lack of internal recreation space and purposeful activity," the report said.
Prisoners at the sites were denied access to dining facilities and were required to eat their meals in their cells, next to uncovered toilets, the report said.
While a new dining facility is being built at Invercargill prison, remand prisoners will not be allowed to eat there because they automatically carry a high-security status.
It said the lack of activities for remand prisoners was not limited to just Manawatu and Invercargill prisons, but was also evident at Otago Corrections Facility and, to a lesser degree, Arohata Prison near Wellington.
The Department of Corrections said it had increased the courses available to remand prisoners, and Invercargill prison had increased the number of staff working in its remand unit.