A woman who fantasised about killing her own children was allowed to work undetected as an early childhood teacher for years.
The revelation comes as the Teachers Council pushes for universal registration of early childhood teachers, saying the sector lacked much-needed "safety nets".
A Human Rights Tribunal decision shows that, despite medical staff expressing alarm about the woman working with children, no attempt was made to remove her from her job.
The woman, who is not named, had serious mental health problems, including fantasising about abusing infants and making suicide pacts in which she planned to kill her own children.
She attempted to suffocate and drown one of her own children and placed sleeping pills in lollies she fed them, the tribunal decision shows. She no longer has custody of her children.
Her history was known to medical professionals in early 2006, one of whom noted in her records: "Can this be addressed, working as early childhood carer!!"
Yet for at least two years, the woman was able to continue working as an early childhood teacher. She finally quit her job in 2009. There is no indication the childhood centre was ever told about the potential risk she posed to children.
None of the responsible organisations approached by The Dominion Post - including the Teachers Council, the New Zealand Educational Institute, Child, Youth and Family, and Ministry of Education - could find any record of the woman.
But the ministry said that, since 2002, all carers working in early childhood centres should have been police vetted.
Teachers Council director Peter Lind said that, unlike in primary and secondary schools, many early childhood teachers were unregistered, making them difficult for authorities to track.
If the woman was registered, her mental health and potential risk to children would have been flagged, he said. "But early childhood education still doesn't have the safety nets necessary."
The revelations come as the Government tries to pass an omnibus child protection law, which includes compulsory vetting of the 376,000 state employees who work with children.
Details of the woman's history were recently released in a tribunal decision concerning a privacy complaint she lodged against her ex-partner.
She alleged her ex-partner had improperly acquired her medical records through an acquaintance who was a nurse and used them to blackmail her into relinquishing custody of their children.
But the tribunal dismissed her claims last year and said it was clear the woman - fearing she had attracted the attention of Child, Youth and Family - had asked the nurse to acquire the records herself.
The woman's testimony had an "air of unreality" and she was "lacking in candour".
The tribunal has prohibited the publication of the names of anyone involved in the case.
From the decision, it is unclear which childcare centre employed the woman or whether she has continued to work with children.
A lawyer for her ex-partner said he understood the woman was never registered as a teacher and had since stopped working in early childhood care.
"But I'm sure nobody [at the early childhood centre] ever knew about these details."
The woman's lawyer said he was unable to reach his client and therefore could not comment.
The district health board that held the woman's records also refused to comment.
Under privacy laws, medical professionals can disclose patients' records to help prevent or reduce a "serious threat" to another person, or to preserve public safety.
- The Dominion Post
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