The majority of 23,000 sexual violence incidents reported to police during the past five years were experienced by children or young people, according to a new Ministry of Justice report.

It reveals that for every 100 sexual violence incidents reported to the police, only 31 made it to court, 11 resulted in a conviction and six in imprisonment.

The report, Attrition and progression: Reported sexual violence victimisations in the criminal justice system, which was released on Friday, analysed 23,739 incidents that were reported between July 2014 and June 2018. The figures will now be updated annually.

Hannah Peters Under-Secretary to the Minister of Justice (Domestic and Sexual Violence), Jan Logie said for too long, too many people have faced barriers accessing the justice system. Everyone deserves to live free from violence and to get the support and resolution they need when they’ve been harmed, she said.

It states that sexual violence is prevalent in New Zealand, with a quarter of adults experiencing it sometime in their lives. However, only a small proportion were reported to police, and of those reported, a smaller proportion still resulted in conviction.

The majority of victims were females and the incidents involved someone they knew.

DAVID WHITE/STUFF Prime Minister Jacinda Ardern announces $320m for family and sexual violence support services.

About 55 per cent were for indecent assault offences and 43 per cent were for sexual violation (including rape). Indecent assault - any unwanted or forced sex act or behaviour - was reported by 67 per cent of victims aged 17 years and under.

The new data was commissioned by Under-Secretary for Justice (Domestic and Sexual Violence) Jan Logie, to better understand the barriers to prosecution and conviction for sexual violence cases.

It is the first time such a large-scale analysis has ever been done in New Zealand and will be used by the Government to measure its work in the area, which will include a new law that is set to go before Parliament before the end of this year.

A new $320m budget package has been announced to deliver more support services to the one million New Zealanders dealing with domestic and sexual violence every year.

It was shocking that it was the first time the numbers had been crunched and the findings were not good enough, Logie said.

For too long, too many people had faced barriers accessing the justice system, she said.

"We can effectively estimate that across all sexual violence - including those not reported - we have a one per cent conviction rate."

A July Cabinet paper deftly summarised the difficulties and obstacles in the justice process. First, most sexual violence goes unreported, and when it is reported, there are "high rates of attrition" between the police investigation and the trial.

Those who report sexual violence risk being further traumatised by their exposure to the justice system, the report said, as "many aspects of a victim's journey through the system are inconsistent with their recovery".

The new data showed that even intensive efforts from various agencies had not made a big difference in the past 10 years, Logie said.

Ten agencies were working together to transform the system but there was still a very long way to go, she said.

The Government has committed to making progress by improving court facilities, providing psycho-social support for complainants and the Solicitor-General had issued new prosecution guidelines.

Further work is underway looking at significant changes such as the role of a jury in sexual violence case, how the law defines consent in the context of sexual offending and what alternative resolutions might work safely and appropriately outside of a courtroom.

The Government will now try to make sure the law was up to scratch and aimed to pass a new law, to reform the sexual violence legal framework, before the 2020 election.

She said a raft of measures in the law would reduce retraumatisation, focus trials on facts rather than breaking down complainants, tighten rules around evidence of sexual history, recording evidence and providing certainty for judges to intervene.

The Government had to be accountable for the impact of its actions, she said.

"These figures do not make for happy reading but it is crucial we understand where we are at ... to be sure that our efforts to change things are working, so we will be able to measure progress in the future."