At least two government departments have drawn up secret lists containing the names of people accused of abusing children in state care over 50 years.
The lists contain "potentially hundreds of names", according to a source familiar with the process, and were drawn up partly to identify individuals accused of multiple sexual violations at different children's homes.
However the lists have not been given to the police or the Royal Commission into state and faith-based abuse, because of court action sparked by concerns over privacy and possible retaliation against those who named them.
The Government, which argues it should be allowed to forward such information, has won the right to have the issue heard at the Court of Appeal.
The Royal Commission has forecast using its powers under the Inquiries Act to gain access and is understood to be exploring other ways to obtain the information.
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Names of alleged abusers were compiled by Ministry of Social Development and Ministry of Education researchers investigating claims of historic abuse in state-run institutions from 1950 to 1999, the period the Royal Commission was set up to investigate.
The details would prove a valuable investigative resource to the commission and probably also to the police, who are carrying out new investigations into abuse alleged by children in state care.
Former state wards interviewed by the Herald have spoken of individual staff members alleged to have abused children in care who were later encountered at other institutions, where they went on to abuse others.
"They shifted perpetrators from one place to another," said former state ward Tyrone Marks, who is on the Royal Commission's Survivor Advisory Group. "It left the paedophiles to continue to do their stuff.
"And when they caught them again, they sent them to some other home."
The Herald learned the highly confidential lists of completed claims containing names of alleged abusers were compiled at the Ministry of Social Development and the Ministry of Education. It is believed other agencies - such as the Ministry of Health - have undertaken similar work.
Someone familiar with the process said names were compiled as claims of historic abuse were researched.
"You want to know if there are allegations against someone by a number of people," said the person. "It doesn't mean an allegation has been proved, just the allegation has been made."
Databases across the agencies involved in claims of historic abuse in state care held "potentially hundreds of names", said the source.
University of Auckland senior lecturer Dr Stephen Winter researched the claims process at the Ministry of Social Development and wrote in an academic paper published last year: "The ministry … has a database of settlements with information about particular complaints and offenders … (and was) able to make 'similar fact' assessments in some cases."
Ministry of Social Development deputy chief executive Stephen Crombie confirmed it held names of those who worked in state institutions who were alleged to have abused children, emotionally, physically and sexually.
He said police had approached MSD for information on specific people and where possible details had been provided.
Ministry of Education deputy secretary Katrina Casey also confirmed her ministry had recorded names of those alleged to have carried out abuse as part of its historic claims process.
She said the information had not been passed to the Royal Commission, although information was provided to police when there were safety concerns and when it did not breach the existing High Court orders.
Before late 2018, Crombie said MSD had told police of physical and sexual abuse allegations in response to requests.
But a High Court decision halted the practice, blocking government departments from providing police with court documents from historic claims proceedings - or the allegations in the documents - without the court's permission or claimants' consent.
Justice Rebecca Ellis blocked government departments from passing details to police after a "failure of process" saw statements of claim filed with the court passed on to detectives without permission or even claimants being told first.
Those claimants had raised concerns about "deeply personal and intimate events" being shared without their permission, and fear of retribution - including concerns by serving inmates it would leave family members vulnerable.
Ellis said there were also "powerful" obligations on the Crown to keep children safe, to investigate alleged criminal offending and prosecute alleged perpetrators.
In attempting to balance the claimants' rights against the Crown obligation, she said information could not be passed on, unless it was necessary to protect children directly at risk.
Lawyer Sonja Cooper, whose firm acted for the people whose details were passed to police without permission, said it would be helpful for the Royal Commission to have access to "any material held by the Ministries which catalogues perpetrators of abuse".
Cooper - whose firms handles more than half of all those taking claims - said her firm had never had access to the lists of abusers and had never been directly told they existed.
A spokesman for the Royal Commission confirmed the information contained on the databases had not been supplied.
He said the Inquiries Act - the law under which the Royal Commission operated - had the power to obtain information it considered "relevant and appropriate". It had the ability through the law to protect survivors by restricting access to information it held.
In a video on the Royal Commission website, its lead lawyer Simon Mount said extensive legal powers would be used to get information needed for the inquiry.
"If we feel anybody is withholding information or withholding documents, we will use our compulsory powers to make sure we do get to the truth."
The Royal Commission is working out protocols and systems for collecting information about state and faith-based abuse. The Herald has confirmed it has already passed on information to police about alleged abusers, which had led to investigations into abuse against children in state care.
Further, police national criminal investigations manager Detective Superintendent Tim Anderson said fresh complaints had been received from those who were patients at the former Lake Alice psychiatric hospital.
"Those complaints are currently being investigated and relate directly to the sexual abuse allegations."
Lake Alice is understood to be high on the Royal Commission's agenda. There are multiple accounts from former state wards of abuse suffered at the former psychiatric hospital.