A coroner says it is of extreme concern that nothing was done to fix an identified suicide risk in the old Mt Eden prison for 15 years before it was shut down.
The death in 2009 of Glenn Mills, who was accused of deliberately infecting people with HIV, has officially been ruled a suicide.
Coroner Katharine Greig says 10 other inmates had killed themselves in their Mt Eden jail cells since 1996 in the same way Mr Mills did.
She says coroners had repeatedly flagged the risk from window bars in cells, and the failure to address that was a serious omission by the Department of Corrections.
Elsewhere in her report, the coroner said Mr Mills wasn't given his anti-depressant medication on several occasions before his death and such a system failure was unacceptable.
Recommendations include better staff training and assessment of vulnerable inmates.
The Department of Corrections said in a statement that it can be difficult to stop someone who is determined to harm themselves.
The department said it recently began mental health screening of inmates and is developing a suicide prevention strategy.
The Prison Reform Society says the Corrections Department should make a commitment to new practices in light of the coroner's criticism.