The Milburn jail was one of three prisons in the ''needs improvement'' category of the Government's Prison Performance Table, released by Corrections Minister Anne Tolley yesterday.
All 17 New Zealand prisons were measured against each other in areas including security, assaults, drug tests and rehabilitation programmes.
The Otago Corrections Facility (OCF) was listed as effective under rehabilitation but below par on internal procedures, which covered assaults on staff and prisoners, justified complaints and the percentage of positive random drug tests.
Its high number of assaults let it down, Corrections Services national commissioner Brendan Anstiss said.
Between October and December last year there were 10 prisoner-on-prisoner assaults at the OCF, three of which were serious, and two non-serious prisoner-on-staff assaults.
Last month, the Otago Daily Times revealed the extent of assaults at the OCF, which were increasing despite extra efforts to protect prisoners and staff from violence.
Assaults at the jail had risen each financial year to 57 in the 12 months to June 30, 2012. There had been at least 125 assaults since the facility opened in 2007.
The prisoner population had increased from 40 in June 2007 to more than 400 in January this year, but the ratio of assaults to prisoners had also steadily increased.
In the 12 months to June 30 last year, there was an assault for about every seven prisoners, including the 60-odd on remand.
Dr Anstiss said prison manager Jack Harrison, at present on annual leave, was working towards reducing assaults.
''We have a zero tolerance approach to assault and under no circumstances tolerate assaults against staff, but at the same time we're realistic. The prison manager is dealing with 400 people put in prison for good reason, and prisoners being prisoners, they will fight amongst each other.''
The prison had adopted a programme to eliminate violence, staff had extensive training and the types of protective equipment available were being reviewed, as were the activities prisoners engaged in.
''I'm confident that all of these things will see OCF and Jack and his team move up that scale pretty quickly,'' Dr Anstiss said.
No prison was ranked in the ''exceptional'' classification.
Mrs Tolley said the performance measures were introduced to enable greater transparency and accountability to taxpayers.
Prison performance
Exceeding: Invercargill, Manawatu, Mount Eden, Tongariro/Rangipo, Waikeria, Whanganui.
Effective: Arohata, Auckland Women's, Auckland, Christchurch Men's, Christchurch Women's, Rimutaka, Rolleston, Spring Hill.
Needs improvement: Otago, Hawkes Bay, Northland.
