The prison officers' union says the chief ombudsman does not understand how bad Corrections' staff shortages are.
Peter Boshier has told a select committee there was an unacceptable culture of containment, with some prisoners locked up for 23 hours a day. He also said pepper spray was being used in a way his office found "offensive".
But Corrections Association president Floyd du Plessis says pepper spray is a necessary tool to protect guards from violence, particularly with a shortage of officers on the ground.
Boshier told the select committee there was an unacceptable culture of containment in many prisons - with situations of no visits, meaningful human contact or rehabilitation - which had continued since the pandemic response.
"One might say 'well, everything's changed' - we've been able to put that to the test to quite some extent," he said. "Corrections is glacial. Getting change within this organisation is like pushing a barrel of concrete uphill, and when I talk about Auckland Prison I think you'll see what I mean."
Floyd du Plessis says Corrections' recruitment drive is working, but it's now a race to keep up with the increasing prison muster. As of 31 December there were 9115 people being kept in prison, up nearly 1500 on two years ago.
"Unfortunately, the language that [Boshier] used is very emotive and he's making it sound as if this is a widespread problem," du Plessis told Morning Report on Friday.
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"During Covid, yes, it did happen. It happened for a number of reasons: a) staff shortages, b) due to the Covid situation it was needed. It worked, and we had results from that.
"Yes, some of that has continued, but what's being slightly missed in this entire story is the use of it is very narrow. So, it's only being used in a very small area of Auckland Prison, not the entire prison. It's not widespread.
"It's also a case of it's being used a) because, yes, there are staff shortages, and we're we're working in an industry like yesterday's events."
Du Plessis agreed that change in Corrections could be "too slow", but it often had to be due to safety concerns.
"The units he's talking about in Auckland, one of the problems is he compared that to another prison that is a minimum security prison. You can't do that.
"So the Auckland prison, the units that he's talking about, the prisoners in there are isolated for a number of reasons. One of those, yes, is staff shortage. We can't have everyone do everything.
"At the same time, we're also talking about prisoners that you've got 50 prisoners in an area, to get them all out takes time. A lot of those prisoners in that specific area don't like mixing - as soon as they're out in some numbers, they attack each other and they attack us. And so there's a need to keep them separate."
He said the union has asked for alternatives, like safer types of pepper spray. Another helpful initiative would be to have more beds spread out across the country, he said, so violent prisoners could be kept apart.
Corrections itself also pushed back on the ombudsman's comments, deputy commissioner for prisons Neil Beales saying there was "no reluctance to change".
"But that is going to take time in order to recruit people to these roles that we need to fill."