Convicted fraudster Alex Swney is calling for a total overhaul of the prison system and has written to the Prime Minister and Justice Minister demanding action.
Swney told Newshub Nation the system is broken and prison is frightening and does nothing to prepare inmates for the outside world.
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"We need to acknowledge the reality of this," he told Newshub Nation.
"I'm sorry - we can't hide behind these platitudes. I'm sorry - the place is broke."
In 2015, the former boss of Auckland's Heart of the City business organisation was sent down for tax evasion and fraud involving more than $4 million.
"If it wasn't so frightening it would be fascinating. It is this unreal environment that you just can't imagine it; it attacks you in every way.
"We like to think it's rehab - it's not. It's just a miserable, punitive, negative experience."
Swney served 23 months of a five-year, seven-month sentence.
"I know there will be people out there who say, 'Oh look, you've done wrong and if you can't do the crime don't do the time,' but the problem is it's supposed to be something that springboards these people back into society as constructive members and does anything but."
Our prisons are at bursting point. The muster has topped 10,000, and inside tensions are high, with inmates routinely double-bunking. About half of all inmates end up back inside within five years of being released.
Swney taught yoga and literacy in prison but says inmates had few incentives to better themselves.
"We need to look at that prisoner and how they ended up there. Their path there was inevitable in so many cases."