New Zealand's prison population continues to reach all-time highs, forcing officials to get creative in juggling the numbers.

Some inmates share accommodation, while others are being moved around the country and this has attracted criticism, as those behind bars find it harder to see their family or their lawyers.

The county's prison muster reached an all-time high of 9436 on April 16.

By last week it had fallen to 9325, still well above the 9000 figure it crossed for the first time in August.


University of Canterbury criminologist Greg Newbold said harsher law and order policies, such as making parole and bail harder to obtain and three-strikes legislation, mean the numbers won't be heading down anytime soon.

Double-bunking would also affect inmates' rehabilitative efforts and Dr Newbold knew of one struggling to undertake tertiary study.

"He's having a hell of a job getting his study done because he's got a cellmate who wants to play radio or his guitar," he said.

"If you've got an inmate who's really doing his best to improve himself and getting out of prison a better person, we're making it hard. We're putting obstacles in his path."

Prisoners, some of whom were yet to be convicted or go through the court process, were also being moved around and sometimes were not staying in the closest prison to home.

For those who needed legal advice or had to sort out their home affairs, this was a hard, particularly if an inmate's family can't visit.

"When you're on remand you need visits because you need people to do things for you... Someone's got to clean up all your business for you," Dr Newbold said.

Sociologist Jarrod Gilbert echoed Dr Newbold's concerns about remand prisoners.

"If you're removed from your family and you lawyer, clearly that's a problem."

He and criminal lawyer Michael Bott both expected the prison population to keep rising with the tough law and order stance.

Over-crowding would also create stress and anxiety.

"There must be an increased risk of violence, sexual abuse, sexual assault, further straining of resources and a loss of privacy," Mr Bott said.

The Department of Corrections expects numbers to reach 10,000 by 2017.

"Prisoners numbers are dependent on factors outside Corrections' control, including legislative changes, judicial decisions, policing trends and crime levels," said Corrections' national commissioner Jeremy Lightfoot.

"The current increase is due to more people being held in prison on remand than was forecast.

"While we have been able to manage muster pressure within our existing capacity by optimising our use of prison accommodation through national oversight, deferring planned maintenance work, reconfiguring prison units, these initiatives are not sufficient to manage future increases."

Mr Lightfoot said the department was looking at ways to house the increase in inmates.

He also said double-bunking had worked well in New Zealand, where only about 30 per cent of the muster shared cells, compared with 70 to 80 per cent in South Australia.

In response to suggestions Government policy was having an effect on numbers, Justice Minister Amy Adams said the Government strengthened bail and parole laws to improve public safety.

"Our reforms centred around ensuring our laws are holding offenders to account and keeping the right people in prison," she said.

"While ministers are monitoring increases in the prison populations, as Justice Minister my focus is on the prevention of crime and some of the broader causes that drive people to criminal behaviour.

"The investment approach to Justice which I launched recently is designed to ensure that investments made by Justice sector agencies on preventative activities is focused on achieving the biggest impact, through a combination of data analytics, research and application of findings."