Solitary confinement made people "lose access to your sense of yourself".
He said there were five types of confinement.
Directed segregation is used for the safety and order of the prison, directed protective segregation is for the safety of the prisoner from others, and can be voluntary, and cell confinement can be used following a disciplinary process.
Research within the mental health setting in New Zealand suggests there are already existing alternatives to solitary confinement.
There is also the use of at-risk units and de facto solitary confinement, which prisoners can be placed in due to their usual "regime".
"The effects of solitary confinement can be severe and long-lasting. Solitary confinement can cause extreme physical and psychological pain," Lamusse said.
"Isolation has been found to cause anxiety, depression, and psychosis. People in solitary are also much more likely to take their own lives."
According to the report, solitary also has concerning social side effects.
"People coming out of solitary are more likely to use violence against others and themselves, creating an even more dangerous prison environment."
There are four recommendations in the report. They are that the legislative framework allowing solitary be repealed, the use of solitary be prohibited in any prison, the right to time out of cells be enshrined, and that alternatives to solitary confinement are established.
"Research within the mental health setting in New Zealand suggests there are already existing alternatives to solitary confinement," Lamusse said in the report.
"A recent study which used alternatives to solitary confinement to address violent behaviour of prisoners in the New York City jail system led to a substantial decrease in the rate of self-harm."
The programme gave prisoners with serious mental illnesses who had broken jail rules various therapeutic activities, normal hours of unlock, and substantial opportunity for social interaction.
Solitary is inherently inhumane, depriving people of their basic need for social interaction.
Lamusse said such an approach could help reduce the number of people in solitary confinement in New Zealand and lead to better mental health outcomes, though he said treatment of mental illnesses and problematic behaviour tended to be more successful in non-carceral settings.
"The best alternative to solitary confinement and its ill-effects is not to imprison people in the first place . . . therapeutic alternatives to solitary confinement must be established, including alternatives to imprisonment."
He said the data showed solitary confinement negatively affected prisoners' rates of reoffending, and had no effect in reducing prison violence.
The report showed the "undeniable necessity" for solitary to be abolished, Lamusse said.
"Solitary is inherently inhumane, depriving people of their basic need for social interaction. It can also, in certain circumstances, amount to torture."
People coming out of solitary were "more damaged and more likely to hurt others".
"There is absolutely no justification for its use."
However, Corrections' chief custodial officer Neil Beales said solitary confinement was not used in New Zealand prisons.
"Many of the people that we manage in prisons are dangerous and can be extremely violent."
In recent years there had been an increase in the prison population, while Corrections had also had to manage increasingly violent prisoners to keep staff and other prisoners safe.
"We have a duty of care to our staff, and other prisoners in our custody, and must keep them safe from harm. We will not compromise on safety and risk death or serious injury to staff or prisoners.
"Where a prisoner's behaviour presents a risk to the security of the prison, the safety of others, or themselves, they can be lawfully denied association with other prisoners or groups of prisoners temporarily. This is lawful under sections 57 to 60 of the Corrections Act 2004. Some prisoners ask to be segregated due to the very real threat of intimidation and violence posed by gangs in prison."
Segregation was used across all corrections jurisdictions to manage violent, disruptive, and dangerous prisoners, and to protect those at-risk of self harm or harm from others. It was one of many mechanisms used to keep those in custody safe, and prisoners were removed from segregation at the earliest opportunity.
"At all times segregated prisoners continue to be provided opportunities for exercise, access to visitors, mail, telephone calls and other minimum entitlements set out in the Corrections Act. They also have regular and ongoing contact with custodial and health staff, as well as mental health professionals as required."
Nearly 91 percent of prisoners have had a diagnosis of a mental health or substance abuse issue in their lifetime which meant there may be times when a prisoner had to be housed in an At Risk Unit to protect their mental or physical health.
