Figures released by Corrections show Mt Eden Prison isn't the only one in the country that has problems with assault.

The privately run prison has been taken over by Corrections after reports of violence, and an inquiry is underway.

However figures show that in the 2014/15 financial year Hawke's Bay Regional Prison and Christchurch Women's Prison had more assaults per hundred prisoners recorded than Mt Eden.

It recorded 22.8, while Hawke's Bay hit 23.5, and Christchurch women's 37.

The assaults range from serious assaults, including sexual assault or assaults causing injuries that require hospitalisation, to behaviour like spitting, or pushing past a Corrections officer.

But the Corrections Association says figures that show some state-run prisons are just as violent as Mt Eden can't be relied upon.

Industrial officer for the Corrections Association Beven Hanlon says all the controversy around SERCO running Mt Eden is based on the fact they're under-reporting serious assaults.

He said an example is an inmate whose arm was broken so badly it needed surgery, but the assault wasn't reported.

"If Serco are hiding the incidents that most normal people would deem severe and serious, you can bet your bottom dollar that they are also doing the same with the very small minor ones."

Mr Hanlon said women's prisons often record high levels of assaults, but they're low level.

He said better reporting also contributes to the higher numbers.

"They don't tolerate is essentially so they report it. Remembering because of their very low numbers, one or two incidents pretty much put their stats through the roof."