The Chief Ombudsman's report into four New Zealand prisons highlights violence, bullying and even a lack of privacy when using the toilet and access to dental services.
Chief Ombudsman Peter Boshier published reviews of Christchurch Men's, Rolleston, Arohata and Manawatu prisons on Tuesday.
The inspections were carried out this year under the Optional Protocol to the Convention Against Torture (OPCAT), which puts international obligations on New Zealand to ensure people held in detention are treated humanely and with decency and dignity.
"People in detention are among our most vulnerable citizens and we must meet international standards for how they are treated," Mr Boshier said.
The key findings at Christchurch Men's Prison was that 60 percent of those surveyed said they had been bullied; 49 per cent had been assaulted, but only 27 per cent reported anything to prison staff; 11 per cent had been sexually assaulted; and 23 per cent said it was easy to get drugs into prison.
Mr Boshier said conditions in the at-risk unit in Christchurch were unacceptable.
"The environment does not provide suitable accommodation for distressed individuals assessed as likely to commit self-harm or suicide, or who may be suffering serious mental health issues.
"The prison's efforts to improve the environment and treatment [after previous review in 2013] were superficial."
The report noted the tie-down bed in the prison's at-risk unit had been used for 15 hours on one occasion and reasons for its use were "questionable" as records "did not indicate a life-threatening situation".
On two occasions, a prisoner who had been suspected of swallowing an article while at work was segregated. He was denied access to a shower, compelled to wear strip clothing and not allowed to wear underwear for a total of nine days. "Nothing was found on either occasion," the report said. "The Prison had not complied with policies and procedures for the management of such cases."
All cells were were subject to CCTV monitoring, including when going to the toilet, which Mr Boshier said "amounted to degrading treatment or punishment for the purpose of the Convention Against Torture".
Evening meals were distributed as early as 3.15pm and breakfast at 8.30am, resulting in a gap of over 17 hours between meals, he said.
Prisoners advised that access to the phone was controlled by gang members who extorted an 'access fee', which Mr Boshier said should be urgently addressed.
Meanwhile, in Arohata Prison, in Wellington, poor site security, including open doors and not properly checking ID, had to be addressed, and there was a lack of access to dental services for prisoners.
In Manawatu Prison the key issues involved "gang activity, bullying and contraband introduction", while at Rolleston Prison, cameras covering toilets and the need for privacy screens had to be addressed, Mr Boshier said.
Minister of Corrections Kelvin Davis welcomed the inspection reports. He said the review of Christchurch Men's Prison was unacceptable.
"If we want to reduce the prison population, we can't just lock people up - the focus has to be on rehabilitation," he said.
"For this to be successful we must have the right culture in our prisons and the facilities have to be up to scratch."