Social workers say they are being unfairly criticised for the way they handled the teenage boys who boasted online of having sex with underage drunk girls.
A review by the chief social worker of the so-called Roastbusters case, released yesterday, has found social workers initially took complaints of rape seriously but then decided the sex was consensual.
The highly critical report set out a host of failings on the part of Child, Youth and Family, from early 2011 until the end of 2012.
Over two years, the agency got complaints from six girls who named the same boys.
But once the social workers formed the view the girls had consented, it was then decided what had happened was not abuse.
Some staff thought underage girls had a right to make risky decisions about sex.
Russell Smith - who worked with sexual offenders at Korowai Tumanako - said it made grim reading.
"I certainly would expect a practising social worker to know what consent is. That would be right at the top of the list, especially when it comes to harmful sexual behaviour."
The report said social workers did not understand the difference between normal and harmful teenage behaviour - and recommended more training in that area.
Mr Smith said that should not be needed.
"I'm really interested in how they made a decision on how that child, or that young person, said it was consensual," he said.
"That's a bigger issue for me because these are social workers that are trained, supposedly, in social work."
The review said staff were influenced by misinformation and miscommunication in deciding what had happened, but did not give details.
It said even though the police did not charge any of the boys, Child Youth and Family could have intervened.
CYF staff under 'unreasonable' pressure
But chief executive of the Association of Social Workers, Lucy Sandford-Reed, said those on the frontline were not to blame.
"The whole institution of Child, Youth and Family is inadequately resourced, and is putting expectations on staff that are unreasonable and don't allow social workers to work in a way that is set out in our code of ethics."
The review said social workers needed more training to understand teenagers' behaviour.
It also acknowledged that at times they had an enormous workload.
Ms Sandford-Reed said calling for extra training, however, was easier said than done at Child, Youth and Family.
"[Social workers] often don't get back up to do training, so if you go on a training course for two days, there's no one there to pick up your caseload and work with those people."
Two years ago, Auckland woman Jessie Hume sent a petition to the government with over 100,000 signatures, calling for action in the Roastbusters case.
She acknowledged the strain social workers were under, but said the latest criticisms were another unacceptable blow to the girls involved.
"How is it possible that these girls were failed for everyone responsible for their safety?
"They were failed by the police and the justice system, they were failed by CYFs, who were they supposed to turn to?"
The review also pointed out big problems with how Child, Youth and Family recorded information.
It said because staff did not log details into the system properly, complaints were never followed up on - and ongoing, concerning behaviour of some involved went unnoticed.
Like many other reports on Child, Youth and Family, this one again recommended it worked more closely with other agencies.
The Children's Commissioner said the social workers involved did not have the skills to deal with the serious situation.
Russell Wills said a lot of attitude and system changes were needed.
"We need to make sure that men's attitudes towards woman are appropriate, and then when this does occur, we need to make sure our social workers - who are generally good people who work their tails off - do have the skills, times, systems and supervision so they can work these cases well, get good outcomes and keep these kids safe."
Meanwhile, the Labour Party's children spokeswoman Jacinda Arden told Morning Report the review of the case showed social workers did not appear to understand the issues around consent.
"Some could argue that in this case, the police weren't either. Consent was actually irrelevant - these children were underage. But I think for CYF, they did take a bit of a steer from the police, but their roles are completely different."