Prison inspectors had to intervene when two inmates seriously assaulted another inmate at Arohata Prison and staff did nothing to protect the woman.
The Officer of the Inspectorate visited the prison in September 2020 to review conditions, function and safety at the facility.
The report, released last week, detailed the incident where two women seriously assaulted another inmate.
"Staff did not respond appropriately and no action (to ensure the victim's safety or to punish the perpetrators) was taken until the inspectorate intervened," the report stated.
The victim had previously told staff the other inmates were threatening her and making her feel unsafe.
The inmate told the inspectorate she had asked for voluntary protective custody but her request was denied. The woman said staff had not taken her concerns seriously.
After the assault she was taken to hospital, but on her return, she was put back in the unit where her attackers remained and no action had been taken.
The report said she was later placed in voluntary protective custody, after the inspectorate got involved.
After intervening, the women were then segregated and one had a misconduct charge laid.
The inspectorate also noted the prison did not have a dedicated Site Emergency Response Team (SERT) to respond to serious incidents of violence and disorder.
The facility said it intended to use Rimutaka Prison's team, but the report said this would be unlikely to offer a timely response because of the geographical distance.
Interviews conducted as part of the report found most women felt safe, but wāhine from the Upper Prison, where the assault occurred, said they were bullied by other inmates.
"Four of these wāhine told us they felt bullied by particular prisoners. They said leaving the unit to go to work every day helped them cope.
"Inspectors reported the issue of bullying to prison management."
Chief Inspector Janis Adair also found parts of the health service were not up to scratch and the budgeted hours for the medical officer and dentist were not adequate for the prison population.
"It was disappointing there was no primary mental health support and limited trauma counselling available," she said.
"Similarly, the mothers with babies unit was still not being used and improvements had not been carried out. This concern was raised in our 2018 inspection of Arohata Prison."
The report also said the Intervention and Support Unit (ISU) was not a suitable environment for prisoners who were at risk of self harm or mentally unwell.
The prison was also using rooms that were not safe for at-risk prisoners when the allocated unit was full.
However, Adair said sanitary and toiletry items were available to wāhine and they had good access to midwifery support and clothing.