It follows revelations about treatment some inmates at Auckland Women's Prison went through.
He's scheduled to front a press conference at 5pm.
Kelvin Davis says he wanted and expected better from Corrections.
Kelvin Davis is taking aim at his department over its failure to answer accusations of "cruel and inhumane" treatment of inmates.
The inmate was unlawfully held for months in a segregation unit.
Corrections chief Jeremy Lightfoot revealed new details about the six-day stand-off.
Gassing prison cells is being defended as the least barbaric way to get unruly inmates out of their cell.
"That is something that no western nation should ever have to put its hand up and admit."
An asthmatic woman is repeatedly pepper sprayed and has to show her used sanitary products to male guards, RNZ reveals.