More concerns have been raised over the treatment of the country's prisoners amid a Corrections staff crisis.
Friends and family have written to Newshub saying it's inhumane their loved ones are spending hours in lockdown.
Newshub's been told some inmates at Rimutaka Prison have been locked in their cells for up to 28 hours at a time.
President of the Canterbury Howard League for Penal Reform Cosmo Jeffrey has done time. He knows first-hand how it feels to be locked up for hours on end with no exercise and no sunlight.
"I've been locked up for 24 hours, or more, in a day and it puts incredible pressure on the whole jail but also in the intimate confines of the people involved," Jeffrey said.
Newshub understands that is the reality for some at Rimutaka Prison, where we are told some inmates have, at times, spent 28 hours straight locked in their cells.
Jeffrey said that's simply not right. The United Nations said any more than 22 hours without meaningful contact is considered solitary confinement.
"It just creates friction, which often turns to aggression, then we have violence, and before you know someone's up on a charge and then they get more time added onto their sentence," Jeffrey said.
In a written statement, National Commissioner Leigh Marsh told Newshub inmates at Rimutaka Prison are getting their minimum 1.5-hour entitlement out of their cells daily, and a number of units are running normal 8-9 hour unlock times.
However, some may be let out in the morning one day and then not until the afternoon the day after.
Corrections told Newshub it understands the impact and is working towards changing the practice in the coming months.
"It's locking the problem away, but it's not solving anything," Jeffrey said.
And while it has room for more prisoners, staffing issues continue to plague Rimutaka.
The country's network of 17 prisons is short 446 guards, but Rimutaka alone accounts for 53 of those vacancies.
"We've even got examples, current recent examples, where even the new staff that have just started ... they've only been in the job a number of weeks and they're already leaving. Because once they hit the floor, and realise the severity of the situation, they decide it's not for them," Corrections Association president Floyd du Plessis said.
Staff issues have other impacts - Rimutaka hasn't been open for family visits since last January.
"It absolutely drives up stress because the prisoners are then sitting in a situation where they're not getting time out, obviously that drives frustration and angst. [And] you're then driving the fact that they're unable to communicate with their family," du Plessis said.
But Corrections told Newshub that increased video calls are available, as well as free phone calls. It hopes to resume physical family visits in the next few months.
