A report outlining the use of isolation practices by New South Wales prison staff - disproportionately impacting Indigenous people - has been criticised as "cruel and inhumane".

The NSW ombudsman's report, Investigation into inmate discipline in NSW correctional centres, was tabled in August and outlines the disciplinary procedures inmates face for breaching one or more of the 71 correctional centre offences.

The report found vulnerable inmates have often been confined to their cells, with a "significant" number (74 per cent) having at least one vulnerability indicator.

42 per cent were First Nations.

The report also found, despite this being prohibited by policy and contrary to the recommendations of the Royal Commission into Aboriginal Deaths in Custody, young Aboriginal inmates have been penalised by being confined to cell alone, and there was "insufficient" regard paid to the withdrawal of phone calls and contact visits as a penalty of last resort.

In one case, Dean, an Aboriginal man with a history of self-harm, was locked in his cell for a day after smoking in a non-smoking area. He pleaded guilty, saying he was "stressed' and was penalised with 48-hour cell confinement.

He was not described as violent or abusive, or how he posed a security threat to the prison, with the report stating: "There were no witness reports or other relevant evidence that supported the position that Dean posed a sufficient threat to justify locking him in his cell pending adjudication."

Inmates are regularly falsely charged, often with multiple offences, with the systemic failures widespread.

The report states: "There is no legislated right of review or appeal other than the theoretical possibility of judicial review."

"That lack of a legislated review right is inherently unfair."

In another case, Kent, an Aboriginal man with a recorded history of self-harm was charged and found guilty of disobeying a direction after he was found holding a razor blade and threatening self-harm.

The witness statement recorded Kent was then cuffed and strip searched.

"There is a systemic failure to follow the requirements of the legislation and the relevant policies in relation to inmate discipline. In some cases, this is leading to unjust outcomes and potentially unlawful decisions," the report said.

The National Network of Formerly Incarcerated Women and Girls (National Network) said they were horrified by the revelations, with member Debbie Kilroy saying the report exposed the "brutality of the prison system" with the number of vulnerable Aboriginal people held in solitary particularly alarming.

"This report confirms what we have been saying for so long: prisons are violent places where officers wield their power with impunity, and nothing changes if nothing changes," Ms Kilroy said.

We must stop pretending that prison officers and the system they operate within are not violent, punitive institutions that routinely punish and torture the people they cage and contain."

NSW Greens MP and Justice spokesperson, Sue Higginson told 7News there has been treatment of inmates "that is tantamount to torture".

"It exposes a very dark underbelly," she said.

In 2022, the United Nations Subcommittee on Prevention of Torture terminated a visit in Australia after being blocked from accessing prisons and mental health facilities in NSW and Queensland.

A report said the independent body "experienced a discourteous, and in some cases hostile, reception from a number of government authorities and officials in places of deprivation of liberty, not in keeping with the collaborative and assistance-based nature of its visit… Such behaviour also raises concerns (as it is assumed to be reflective) of how persons deprived of liberty are treated."

NSW Corrections Minister Anoulack Chanthivong said the system will be overhauled.

"We want to provide our officers with the right training. We are currently reviewing legislation," he said.