Private prison operator Serco sacked 28 staff while running Mt Eden Prison, including a staff member caught sparring with inmates, it says.
It has so far fired 11 staff at Wiri Prison, which it still runs.
The Chief Inspector of Corrections' report into allegations of fight clubs and contraband at Mt Eden Prison - which Serco tried to block - was released today.
It found that fight clubs happened at least weekly and lasted from 15 to 50 minutes, and inmates who refused to take part were threatened with attacks by gangs.
The report was also critical of staff, saying one was caught sparring with inmates on CCTV, and staff played table tennis and pool while fighting went on around them. Staff were also probably the main source of contraband, according to the report.
Serco Asia Pacific chief executive Mark Irwin said the staff member caught sparring was almost immediately sacked, and 27 others were fired throughout the company's time in control of Mt Eden Prison.
He said they had already sacked 11 staff at Wiri Prison, which it has been running since April last year. Two of the dismissals were related to contraband.
"In terms of Wiri, we've got a very strong management team in place there. We've enhanced the training of all of our staff. There is very good oversight from Serco management, from the departmental monitors that are on site."
Mr Irwin said they did not tolerate staff playing table tennis or pool, as the Chief Inspector's report pointed out.
"We're extremely disappointed to have discovered that that happened and are vigilant about that not reocurring in any of the facilities that we operate today."
He said the public could have confidence in their running of Wiri Prison.
"We've got in place a good team of managers and staff, but we are not complacent and we continue to monitor on a daily basis any changes that occur in terms of the prisoner profile, and the risks that may emerge in the prison.
"Our goal is to get ahead of that and make sure that we can continue the level of performance that we've delivered so far, and through that we can re-earn the trust from the public of New Zealand after the incidents at Mt Eden."
He said there had been no evidence of fight clubs at Wiri Prison to date.
The Corrections Department said Serco was redeeming itself with the way it was running Wiri Prison, despite the report exposing wide-scale failings at Mt Eden Prison.
Corrections chief executive Ray Smith said he was surprised at the poor levels of supervision and oversight, as well as the absence of structure at Mt Eden Prison.
But he said they had since made sweeping changes to the way it was run.
He said it was unacceptable that staff got involved through contraband and sparring - and they had also fired a number of staff since taking over.
"It goes to a lack of leadership, supervision, management, training. And I think there are some very good people who work in that prison.
"Because the prison is running very, very well now. I was there on Tuesday and I was very impressed with it. It's not the prison I saw 12 months ago."
He said they had implemented 13 of the Chief Inspector's recommendations, and eight others were still under way.
"Some will take us a little bit longer, we've got some more things to do in the health area to get it right up to the standard we'd like.
"There are some infrastructural things we need to change as well to make the prison run better."
Mr Smith said the number of staff Serco had fired reflected how difficult it was to work in prisons, and how important it was to make sure the right people were in the job.
He said he was at Wiri Prison two weeks ago.
"We've got quite an extensive monitoring regime there, a much stronger one I think than what we had in Mt Eden.
"It's a new jail, it's only been up and going with full muster for a bit over a year and they've got a lot of experienced people."