An independent report into the justice system says that is failing New Zealanders at all levels and requires transformative change that will take a generation.

The report, called A Vessel of Tears and released this morning, is from the Safe and Effective Justice Advisory Group, chair by former National Party Minister Chester Borrows.

It is an interim report that is the culmination of months of talking to thousands of people nationwide about their experiences with the justice system.

It paints a bleak picture of deep dissatisfaction across all aspects of the criminal justice system, and the social neglect, poverty and prejudice that drives people to crime.

The report's key points include:

• Victims of crime often feel "unheard, misunderstood and revictimised", and their experience with the justice system sometimes increases distress; 83 per cent of victims say the system is not safe for victims.
• The number of Māori in the system (16 per cent of the population but 51 per cent of the prison muster) is a crisis, as "the effects of colonisation undermine, disenfranchise and conspire to trap Māori in the criminal justice system.
• Family and sexual violence is "an enormous problem", and sexual assault victims have among the worst experiences; one in five women have experienced partner violence, one in three sexual violence, while 29 per cent of family violence deaths are neglected or abused children.
• Justice processes are confusing, alienating, and unfairly favour those with money and education. Issues include the adversarial system, delays, inconsistencies and difficulties in accessing justice.
• The system focuses on punishment rather than rehabilitation and there is widespread frustration that mental illness, addiction, and drug and alcohol abuse are treated as criminal justice issues, not health issues.
• People feel unsupported and disempowered by the system, and the ability of iwi, communities, NGOs and others to help is constrained by the siloed nature of government services.

"The overwhelming impression we got from people who have experienced the criminal justice system is one of grief," Borrows said this morning.

"Far too many New Zealanders feel the system has not dealt with them fairly, compassionately or with respect - and in many cases has caused more harm."

He said Māori - who make up 51 per cent of those in prisons but only about 15 per cent of the population - bore the brunt of the legacy of colonisation.

"This legacy is actually a gross unfairness and something we should not tolerate in New Zealand.

"There is widespread recognition that at every point in their lives, and over generations, Māori experience disadvantage that increases the risk they will come into contact with the criminal justice system."

Borrows said those who enter the justice system should not just be thought of as innocent or guilty, but also as offenders are often victims of social circumstances.

He evoked the country's response to the March 15 terror attack in Christchurch and asked for more compassion for offenders as well as victims.

"We must continue to have compassion for victims of spontaneous offending who are harmed at random. We also need to better understand the needs of people who have been victimised over long periods with consequences that are shown through their own offending behaviour."

Borrows also said the group had heard about solutions that already existed, and solutions would need a new vision and a cultural shift and could include alternative processes, such as iwi-led solutions and restorative justice.

The Government's Budget announced a number of relevant initiatives including $320 million to tackle family and sexual violence, $98 million to break the pattern of Maori offending, and a $1.9 billion boost for mental health and addiction services.

The group will now put together a final report and deliver it to the Government in August.

"This is a once-in-a-generation opportunity that cannot be squandered," the report said.