A family in mourning is accusing Oranga Tamariki of serious failings after a young mother died while looking after her baby.
They said the baby and her toddler were exposed to drugs and violence, and that warnings signs were clear but social workers did not act.
The woman, in her early 20s, died early this year.
The family had been waiting for months for Oranga Tamariki to hold a review, they said.
"I'm absolutely disgusted. They're absolutely appalling, they could have done more," the dead woman's grandmother said.
Other family members confirmed allegations.
Months on from the woman's death, the family are still trying to find out just what happened, including where she died and how the matter will be handled by the Coroner.
The case has been before the Family Court. The death is with the Coroner and the cause of the woman's death cannot be reported on, nor can the family be identified.
The family of the dead woman said she went with her son to live with a family member, away from her partner, but it appeared the agency did little checking to ensure they were safe.
"If they only can come out and be honest with the family and tell them why couldn't they keep up with their side, keep in contact with my moko and her babies," the grandmother said.
"Nothing would have happened. She would have been still alive now if they looked into that, but they didn't, did they? They failed."
The children should have been a priority case and Oranga Tamariki's processes appeared to have broken down, the family said.
They said the agency's failings included:
- Not acting on concerns about drug use by both the mother and father, and ongoing violence.
- Cancelling meetings with the wider family in September and December 2017, aimed at reviewing safety measures.
- Not checking up on the woman and children.
- Not checking what contact the father was having with the family.
- Never telling wider family if the father had completed any rehabilitation courses.
- Dropping the case early this year after the two children went into the care of other family members.
There had been very limited communication with the wider family by Oranga Tamariki, both before the death and afterwards, the grandmother said.
"They're not saying much."
Oranga Tamariki asked RNZ to seek a privacy waiver from the grandmother, which she agreed to. However, the agency then said it would not talk specifically about the case.
Oranga Tamariki's associate Wellington region manager Maree Meechang said in a statement the priority was protecting the children "in this complex and sad situation".
"These children have tragically lost their mother and their privacy and wellbeing is our paramount concern."
It was is important to let the Coroner consider the evidence fairly and without comment given that investigation, she said.
"As you are aware, a Family Court Judge has already considered the public interest in this story when an application for the publication of court information was made. The application was declined."
It was declined because the Judge said the children's welfare outweighed any "speculative agenda".
The dead woman's grandmother said she was speaking up to hold Oranga Tamariki accountable.
Police records showed the father had a history of violence, the family said. They remained uncertain about the circumstances of the mother's death and were asking the police for an inquiry.
They were not alerted until more than 24 hours after the woman's death, and even then the information was vague, they said.