Police Commissioner Mike Bush says the Roast Busters investigation was not robust enough and no staff will be sacked.

Yet another inquiry in to the "Roast Busters" group - this time in to social services - has been announced.

On Thursday, the Independent Police Conduct Authority (IPCA) said in a report that victims of the "Roast Busters" group had been let down by police. Anne Tolley, who as then police minister ordered the inquiry, said the investigation had identified "serious issues".

The group first publicly emerged in November 2013. Its members boasted online about plying underage girls with alcohol and having sex with them.

ROBERT KITCHIN/Stuff.co.nz Police Minister Michael Woodhouse said the IPCA report showed failures by individual police involved in the Roast Busters complaints.

Now Social Development Minister, Tolley said Child Youth and Family (CYF) would be next under the microscope for its part in the case. Tolley said CYF should also have done better. It would be the subject of a review by the Office of the Chief Social Worker.

"This whole affair is extremely distressing for the girls and their families - and it must not be allowed to happen again," Tolley said.

"Girls everywhere must have the confidence to come forward and know that any complaints will be taken seriously and dealt with appropriately."

ROBERT KITCHIN/Stuff.co.nz Judge Sir David Carruthers releasing the IPCA report findings to the public over the police handling of the 'Roast Busters' victims.

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POLICE FAILURES

The IPCA report found that in its investigation of the group, police failed to pursue positive lines of inquiry. Investigating staff also failed to properly consider all available offences in deciding whether to prosecute the young men.

Officers tended to approach each case on an individual basis, IPCA chairman Sir David Carruthers said.

"In the authority's view, the officers should have identified the connections between the various cases and worked with other agencies to develop strategies to reduce the recurrence of what was clearly unacceptable and, in some cases, criminal behaviour," he said.

"Victims were let down by their failure to do so."

All of the police officers involved treated the young women and their families with courtesy and compassion but contact and interaction with the young men who were the subjects of the investigations, and their families, was inadequate or non-existent, Carruthers said.

"The failure of police to make contact meant the young men's parents were never made aware of several of the incidents and details of their sons' involvement and therefore they were unable to intervene or act to address the behaviour," he said.

Despite the failings, the authority had not found any evidence of ongoing and widespread poor practice nationally in the police investigation or prosecution of child abuse or sexual assault cases.

The IPCA recommended an audit be carried out into current cases being investigated by the Waitemata police child protection team to determine if any individual shortcomings remained, Carruthers said.

It also recommended that police consider if any other practice or policy issues needed to be addressed, either nationally or in Waitemata, and in particular whether more emphasis was needed on prevention.

NO OFFICERS SACKED

Police Commissioner Mike Bush said three of the five officers criticised in the report had been moved to other policing roles outside the child abuse and adult sexual assault teams, but would remain in the force.

"This is a performance issue and it will be dealt with as such."

He could not comment on their new roles.

"With employment law it would be very difficult and improper of me to get into too much detail. But what I can say is that this has been clearly highlighted. The accountability sits with the district commander."

Bush said he was not aware of any work overload issues at the Auckland-based investigative unit where the failures arose, calling it an "isolated incident."

"I have an assurance from the district commander of Waitemata that this was not a workload or resourcing issue. It was a performance issue by a small number of staff at a point in time."

It was too early to comment on what kind of disciplinary measures might take place following the IPCA finding fault with some of the officers, Bush said.

"I am very disappointed in their performance standard as investigators on this matter."

According to the Police Association president, the detectives involved felt they had been made into scapegoats.

Greg O'Connor said the association would have liked the IPCA to take a broader view of what was happening in the area at the time of the investigation.

"They ... were constantly having files coming in which required immediate attention, where people were in immediate danger."

Given what was expected of the detectives, they had done a good job.

"They know full well ... they did their best with what they had. They believe they are being made absolute scapegoats, otherwise someone further up has to take responsibility. It's much easier to blame the people at the bottom."

A FATHER'S RESPONSE

The father of a teenage victim who laid a complaint with police said the IPCA's findings were "reasonable" but questioned the merits of an audit of the Waitemata child protection team.

His daughter had been severely affected by alleged Roast Buster assaults and she had decided not to press charges because of fears of violence, he said.

He believed a parent or guardian should be able to press charges on behalf of their children.

"I think it's pretty hard to be effective doing an audit," he said.

"I think they're all good people and they do a good job but I'm not sure it addresses the problem.

"I don't know that they can really provide protection and support - [sexual abuse] is such a huge problem. I don't think the public really understands how much sexual abuse goes on in New Zealand.

"I think one problem is that young people at 13, 14, 15, you can't just leave them to be fixing themselves when they're ready. It's like asking someone who's damaged to make a sane decision."

He wasn't surprised to hear that police contact with the boys had been minimal.

"When the other [IPCA] report came out the [boys'] families were saying the boys were vindicated. They clearly had no idea what was happening," the father said.

PUBLIC APOLOGY

Waitemata police district commander Superintendent Bill Searle said he was offering a public apology to the women at the centre of the investigation.

"I will arrange to do this in person, depending on their wishes," Searle said.

"I accept the IPCA's findings that some of my staff did not meet the required investigation standard, and did not connect the various cases or work with other agencies to develop preventive strategies.

"They also missed opportunities to communicate with the parents of the young men.

"We clearly let the victims down."

Police Minister Michael Woodhouse described the findings of the report as "extremely disappointing".

"I've received an assurance from Commissioner Bush that the steps that are required to ensure this doesn't happen again are being taken."

Labour's police spokeswoman Jacinda Ardern said the victims involved in the case were children so police should have been treating it as a child abuse investigation.

"Even if the victims didn't want to consider or continue with an investigation, it was really up to the police to do it anyway," Ardern said.

Green Party co-leader Metiria Turei said an independent body had to be set up to make sure police implemented the recommendations.

"The Green Party is calling on the minister of police to immediately establish a taskforce to implement and enforce the changes in police culture, and in the wake of this damning report by the IPCA over the so-called Roast Busters case."

'OPERATION CLOVER'

Last October, police said they would not lay any charges relating to group members because they did not have a reasonable chance of getting a conviction.

That followed a year-long investigation into eight incidents of alleged sexual offending involving seven victims and five suspects.

Police revealed 35 men were assessed as "persons of interest" and 110 girls were canvassed.

Police said 25 of those girls were asked to make formal statements and five did. Those five joined two girls who had already contacted police but whose complaints had languished until media attention put the case in the spotlight.

All but two of the men investigated were aged over 17, with the oldest 25.

Bush said Operation Clover was "a very comprehensive and thorough investigation".