Corrections may be breaching international law with its treatment of high-risk prisoners

The Office of the Inspectorate visited Auckland's Prisoners of Extreme Risk Unit in July last year - then housing 13 men considered to present ongoing risk.

Chief Inspector Janis Adair says they spent most of the time alone in cells.

A lawyer for some of the men in the unit, Amanda Hill, says international law prohibits them from being confined for 22 hours a day.

She says part of that is not just being locked up, but locked up without meaningful human contact - which is they key thing missing in this unit.