Serco has denied putting prisoners' lives at risk, despite leaving entire units unstaffed and unlocked at a facility full of violent offenders.
The private prison operator is under renewed scrutiny following the release of a damning report into its failed attempt at running Mt Eden Corrections Facility.
The chief inspector found Serco had little control over the understaffed prison, and employees regularly brought in contraband for inmates. Corrections monitors knew about the prison's problems, but failed to report it.
Asked by TV3's The Nation how badly Serco ran the prison on a scale of one to 10, Corrections Minister Judith Collins - who originally awarded Serco the contract to run Mt Eden - gave it an "eight or nine".
"They did actually do all of those things to start with - but near the end of the term of their contract, they started to lose control of the situation."
A previously unreleased report from 2009, when the prison was run by Corrections, found many of the same problems existed then. It's believed the fight clubs that emerged under Serco were run by many of the same prisoners.
Serco's Asia Pacific chief executive Mark Irwin said the company didn't cover up anything, and nor was it penny-pinching by refusing to hire enough staff.
"There was no attempt at all, there was no deliberate attempt through the period of our contract for us to misreport anything," he told The Nation. "The inspector found that in his investigation."
Prisoners took advantage of Serco's understaffing, taking part in brutal fights that went unreported. Mr Irwin says the company didn't "knowingly" put lives at risk by having entire units unmanned for up to two hours at a time.
"We had no evidence of the organised fighting until the video evidence arrived," says Mr Irwin.
But he does admit they failed to respond to low staff numbers "quickly enough".
"That's unacceptable. We've admitted that."
The prison staff's union raised concerns about Serco's running of Mt Eden in 2013, including the low staff numbers and how some prisoners were classified. Ms Collins says today is the first she's heard about the union's concerns.
"It's interesting that you received those emails," she told The Nation.
"I have no reason to believe the previous minister [Sam Lotu-Iiga] had access to those. I'd like to see those emails."
She isn't aware if anyone at Serco or Corrections has lost their jobs over the scandal, and wouldn't comment on whether anyone should have. She also declined to comment about the fact one of the Corrections monitors at Mt Eden was now working at the prison in Wiri, south Auckland, which Serco also runs.
Nor does she know if Corrections, which took over Mt Eden after Serco's contract was terminated, will be hiring Serco staff.
"Corrections has told me not all of the Serco staff have been offered contracts," says Ms Collins. "I have to rely on the fact that Corrections is undertaking its due diligence of its staff members."
On Friday, Labour's Phil Twyford said there are reports of fight clubs happening at Wiri. Ms Collins says there's no evidence that's true.
"I've been into the prison, I've had a look around, I've seen people, I've walked through it. I haven't seen those reports."
Serco has a 25-year contract to run Wiri. Ms Collins says there are no plans to cancel that arrangement, despite the company's failings at Mt Eden.
"My choice is that we have a provider, or some providing of some competition."
She says Wiri is a very different prison to Mt Eden, which houses remand prisoners.
"People are on remand because they can't get bail or they haven't yet been sentenced. They have a stay on average of 23 days - it's a very volatile situation, and two-thirds of population in prison is there for violence, and most of those in remand are very violent people."