A man accused of child abuse says it is a "lottery" whether a family gets a proper investigation by Oranga Tamariki (OT) or not.
The children's ministry has admitted to shortcomings in following its own investigations protocol in a case in Northland, and "inconsistencies" at other sites around the country.
Whānau advocates say it is further evidence the system is irrevocably broken, and of families let down.
"I am appalled, that after three years of practice standards, that we could even be seeing this," the chief executive of advocacy organisation VOYCE - Whakarongo Mai, Tracie Shipton, said.
In the Northland case, an internal review sparked by the accused man's complaint, found social workers did not look properly into the boy's circumstances.
"We didn't get talked to, they didn't know who we were," the accused man told RNZ.
A mishandled investigation like his, presented a risk of either not stopping actual abuse, or of breaking up families unnecessarily if OT did not follow due diligence, he said.
"To have them rip your family apart and then tell you that they made a mistake and then have to fight them ... is really wrong."
The man, who RNZ cannot name by law, denies the abuse. The police did not pursue the case after looking at it for about a year in 2018-19.
The man said investigations should not vary according to how good or bad your social worker was, or the lack of support and training they got.
"Do we have an organisation that does what it likes, when it likes, and its own policies and processes really don't matter? I don't know.
"It's a lottery to be honest."
The extent to which ministry social workers don't follow the protocol remains unclear.
RNZ spoke with half a dozen lawyers who work in the family court who said they had little visibility of how the protocol worked since they usually got involved in cases later on.
However, several added that some regions appeared to have effective cooperation between Oranga Tamariki and police, while in other regions many times things did not get done.
Two said that in Northland, OT had improved in the last two or three years.
A lack of scrutiny and oversight was a factor in Northland, OT said.
Its website states: "We must follow the CPP when we are responding to complaints (Police) or reports of concern (Oranga Tamariki) that allege actions or behaviour that may constitute a criminal offence, and where there is a role for each party."
The practice standards are meant to deliver an agreed level of consistent practice at all sites.
Shipton said she already knew of inconsistencies because the young people and their whānau spoke about them.
"Their experiences vary so much that they know there hasn't been a consistency of practice in any aspect of their care - this just highlights that."
All families "had the right to expect that whatever happens for their family will be applied across the country, that good care and good standards of practice will be met whether they are in the North Island or South Island, and clearly that's not evident at this point", she said.
The accused man said the protocol, like so many official documents, looked good on paper.
Shipton said the test of any of the improvements in protocol practices had to be whether the Independent Children's Monitor checked on them, and okayed them.
"We'll certainly be watching anyway, because that's what we owe our young people."
Lady Tūreiti Moxon, who took Oranga Tamariki to task at the Waitangi Tribunal, said the experience of many whānau was their tamariki were taken away and never returned, by dubious means.
"The issue that we have here, is that no one asked the question, no one implemented the protocol," Lady Tūreiti said.
The joint protocol was no guarantee: "The police can only act on ... their part in it - when we're working, you know, it looks like we're working together as a unit, but in actual fact, we're quite independent, siloed government departments," she said.
Oranga Tamariki said improvements would be made next month and in July, with a start of monitoring and national training - on top of existing local training - and more regular meetings with police, to see that social workers followed the protocol.
Lady Tūreiti dismissed this as merely propping up a "broken" system.
"In order for us to fix it, it has to be deconstructed. And our children need to be returned to iwi."
The government last year embarked on what it called a five-year transformation of the children's ministry, including to make it Māori focused.
"It can't work," Lady Tūreiti said.
"The same people who had been working there forever and ever are still doing the same job they've always done."
The test was how many children had been returned to their whānau, she said.
The man accused in Northland said it remained to be seen if the promised monitoring of the protection protocol was more than a box-ticking exercise.