Child, Youth and Family says it's devastated that children raped and abused by one of its carers didn't trust social workers enough to tell them what was happening.
Taite Kupa was found guilty in May this year of abusing six children at a Whangarei CYF home between 2011 and 2013. At the High Court in Whangarei on Friday, the 57-year-old was sentenced to 14 years and six months in jail and must serve at least seven years and three months.
Justice Asher said Kupa had abused the trust of vulnerable children who had been placed in his care by Child, Youth and Family for their protection.
He said Kupa exploited that trust in the worst way possible by forcing himself sexually on the girls, and they would carry the effects of that violation with them for the rest of their days.
Marion Heeney, CYF's regional director for Te Tai Tokerau, told Radio New Zealand's Checkpoint programme that none of the children disclosed the full extent of the abuse to social workers who visited them.
"I know that our social workers that were involved here just feel really terrible, and they're kind of going through all that second guessing - could I have done more?
"But the fact of the matter is: Kupa's done this, Kupa's the one that abused the children. He's the one that has to be held to account for it."
The mother of a girl raped by Kupa says Child, Youth and Family wrongly took the credit for exposing him.
The woman, whose son and daughter were in his care, told the court she was distraught when they told her they were being mistreated.
She said she felt she couldn't trust the government agency. She eventually made a complaint and the children were removed.
The woman said when she told her daughter she'd blown the whistle on Kupa, the girl called her a liar and said social workers had told her they initiated the action.
Child, Youth and Family agrees that it was the mother's complaint that initiated the investigation.