An inspection of Auckland Prison's high-risk unit has found it's unnecessarily restrictive

The Office of the Inspectorate report -- based on a visit in July last year -- says communication with prisoners is poor, leading to a sense of confusion and hopelessness.

The report states long periods of isolation may lead to profound and long-lasting physical and psychological effects, and many prisoners didn't understand decisions made about them, nor the length of their placement.

It also found management of men assessed as at risk of self harm contributed to a deterioration of mental health and wellbeing -- and clinicians had a restricted ability to provide treatment.