An official investigation has found that Child, Youth and Family Services failed to act on more than 200 cases of child neglect last year until it had been notified more than 10 times.
The inquiry by Children's Commissioner John Angus found that in the most extreme case it took 29 notifications of a family before the service determined that a child was being neglected and took action.
It reports widespread frustration by doctors, teachers and other professionals, who reported families to the service and felt that nothing was done about it.
"You are waiting for something to happen, you are waiting for them to be run over in the driveway or burn their arm," one health professional told the inquiry.
"Some days I walk away and I just wish something would happen ... because then I would get some help."
A teacher said: "Kids do us a favour by committing a crime because Youth Justice gets involved and wraparound services are provided."
The inquiry found that, in contrast to huge attention paid to child abuse, official agencies have no agreed definition of the more common problem of neglect.
An inter-agency guide to child abuse produced by CYF defines neglect as "any act or omission that results in impaired physical functioning, injury and/or development of a child".
But the inquiry says this leaves out acts or omissions that risk harm to the child, so CYF fails to intervene in practice unless there is actual harm or a clear threat of physical harm.
"Stakeholders external to Child, Youth and Family perceived a large discrepancy between their thresholds for neglect and the threshold held by Child, Youth and Family professionals," the report says.
Other experts interviewed for the report acknowledge that neglect, unlike abuse, can't always be assessed on the basis of a single incident, so multiple notifications over time may be needed.
But the report questions the 229 cases where it took at least 10 notifications, including 18 cases of more than 20 notifications, before findings of neglect were made.
"An audit of these cases with an extreme number of notifications could be considered to understand why so many notifications were made prior to a child protection response."
The number of cases of confirmed neglect - 4240 last year, or 0.4 per cent of all children - is believed to be "the tip of the iceberg". A survey in 2005 found 9 per cent of adults said they had been neglected in childhood.
Neglect is closely linked with poverty. Confirmed cases last year included 1.7 per cent of all children in the poorest fifth of the country but 0.1 per cent of children in the richest fifth.
Most cases are also linked with either alcohol and drug addictions or mental health problems, such as post-natal depression.
The report urges all agencies to agree on how to recognise child neglect, including "red flags" in the CYF notification system and alerts in the school enrolment system.
CYF head Ray Smith said his agency was "working with other agencies to consider possible improvements to the ways in which data on child maltreatment is collected and reported, including the use of shared definitions or a common understanding for child maltreatment".