The number of Indigenous women in custody has been called "one of the most challenging human rights issues facing Australia".

Key points: Research shows a "disturbing overrepresentation" of Indigenous prisoners

Research shows a "disturbing overrepresentation" of Indigenous prisoners Poverty, family violence, abuse and trauma are often background factors

Poverty, family violence, abuse and trauma are often background factors A top advocate has called for an approach that tackles social and economic disadvantage

Research out today has shed new light on Indigenous women in the criminal justice system in New South Wales.

It found the number of women in NSW jails between March 2013 and June 2019 had risen by 33 per cent to 946.

Almost a third of women prisoners were Indigenous despite making up less than 3 per cent of the population.

Aboriginal and Torres Strait Islander Social Justice Commissioner, June Oscar, said "urgent action" was needed.

"It causes immense distress and disturbance to family and community life," Ms Oscar told the ABC.

Aboriginal and Torres Strait Islander Social Justice Commissioner June Oscar. ( Supplied )

The research report was commissioned by the Keeping Women Out of Prison Coalition (KWOOP).

It draws on the latest data from the NSW prison census and agencies including Justice Health and the NSW Bureau of Crime Statistics and Research.

"There is a disturbing overrepresentation of Indigenous women," said KWOOP convenor Rosalind Strong.

The Coalition is made up of senior academics from UTS and the University of New South Wales, lawyers, representatives from Corrective Services and members of organisations who provide frontline services to women and families affected by incarceration.

The research found the growth in the number of women in prison was due to a 66 per cent increase in the proportion of women on remand, not a rise in crime.

Indigenous women were on average waiting 34 to 58 days for bail, yet in the majority of cases women on remand were not given a sentence.

Advocates are calling for urgent action. ( ABC News )

Mrs Strong said one of the key issues identified in the report was "the unnecessary over-incarceration of vulnerable populations who pose minimal risk to the community".

"There are large numbers of women in prison who are serving short sentences, who are incarcerated for non-violent offences, who are on remand and who pose minimal risk in terms of community safety." Mrs Strong said.

The most common crimes included crimes against justice procedures, drug offences and acts intended to cause injury.

Report contributor Mindy Sotiri said it could be "easy" for women to end up back in jail for crimes against justice procedures, such as minor parole breaches and not turning up to court.

"The conditions are often onerous and women have no support. They may have an intellectual disability. Life can be chaotic," Dr Sotiri said.

However, the NSW Attorney-General's office said there were a range of "diversion" programs which operated in NSW courts.

"The focus of these programs is to divert clients from the criminal justice system into treatment programs that may benefit women’s health and wellbeing as well as reduced reoffending," Attorney-General Mark Speakman said.

"These programs provide access to mental health, cognitive impairment, drug and alcohol and other community services."

The report's authors pointed to a significant increase in Indigenous women being sent to prison compared with non-Indigenous women for similar crimes.

"Indigenous women are overrepresented in the sentenced population, with a 49 per cent increase since 2013 compared to 6 per cent among non-Indigenous women." Dr Sotiri said.

Indigenous women are 21 times more likely to be incarcerated. ( ABC News: Dan Cox )

Ms Oscar said most women in prison had experienced early-life trauma and abuse.

"Poverty, family violence, abuse and trauma are the pathways that lead to women's incarceration and a cycle of reoffending," Ms Oscar said.

"Our criminal justice system is in crisis, but that crisis is not to do with an increased criminality of our people.

"It is caused by unnecessary over-incarceration and a lack of desperately needed investment in community diversionary options.

"The system is broken. We are not," Ms Oscar said.

'Urgent systemic reform'

The Inspector of Custodial Services, Fiona Rafter, expressed concern in January that Indigenous women were 21 times more likely to be incarcerated than non-Indigenous women.

Both KWOOP and the Inspector of Custodial Care said there was an urgent need for greater access to lawyers, changes to bail legislation, early intervention for those at risk of incarceration, alternatives to imprisonment and support to reduce re-offending.

Ms Oscar has backed those calls, telling the ABC "urgent systemic reform" was needed "to provide the necessary supports for children, women, families and communities, and prevent entrenching these problems for the next generation".

"What's needed is a community-led, trauma-informed preventative approach that tackles the entrenched social and economic disadvantage behind most of the minor crimes our women are incarcerated for."

Mr Speakman said he acknowledged the report's call for "greater scrutiny and review of sentencing practices, bail conditions and the role of police", as well as more government resources to reduce recidivism.

He highlighted criminal justice reforms in NSW to the tune of $570 million of State Government investment over the last four years, including giving courts the flexibility of sentencing options that don't involve full-time prison.

"Community-based sentences benefit women offenders because they are able to maintain family and social connections as well as receive programs in their communities that address their offending-related risk factors," Mr Speakman said.

"Ultimately, the reforms aimed to hold offenders to account while reducing their risk of reoffending."

But the report also found an alarmingly high rate of women going back to jail: 87 per cent of women had been in prison before and the majority had children under 18.

Of the 2,760 women released from prison each year about one third, or around 883, become homeless.

The research found homelessness was a major cause of women returning to prison within nine months of release.