New Corrections figures show the controversial Mt Eden prison doesn't have the worst assault rate among inmates - but the union representing prison guards at state-run jails has cast doubt on the numbers.
The figures, released to Newstalk ZB, show the worst overall assault rate in the year to June was at Christchurch Women's prison, with 37 assaults per 100 prisoners.
Hawke's Bay Regional prison was next with a rate of 23.5 assaults.
Mt Eden prison, which has come under the spotlight following revelations of fight clubs and violent attacks on inmates, came in third with a rate of 22.9.
Mt Eden is run by private company Serco, although it is currently under management from Corrections while investigations into the prison take place. It recorded 224 assaults by prisoners on each other or on guards.