Grainne Moss, chief executive of Oranga Tamariki, says New Zealand is leading the way in researching and reporting on harm experienced in state care.

About 12 per cent of Kiwi children experience harm in state care – more than previously thought – new research shows.

Past approaches to measuring the safety of children and young people relied on findings of maltreatment, but new research that the Ministry for Vulnerable Children Oranga Tamariki and the Office of the Chief Social Worker produced jointly took what the ministry called a "zero-tolerance" approach to apply a broader definition of harm.

The report, published on Tuesday, said 85 out of a representative sample of 698 children/young people in state care between July 1, 2015, and June 30, 2016 experienced harm. Given a total of 7360 entered the system over that time, it's likely 929 of them experienced harm.

The research involved manually reviewing the case notes, analysing reports of harm ranging from emotional distress to physical injury.

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While the sampling approach allowed for the overall extent of harm to be extrapolated, other findings such as those relating to demographics, nature of harm, and placement types, were descriptive only.

The authors examined several different placement types, including whānau placement, non-whānau placement, return/remain home placement, group home settings, child family support service placement, and independent living placement.

Of those 85 children/young people who experienced harm, the largest proportion (31) were placed with whānau.

The longstanding whānau-first policy, which prioritises kin-carers when a child is removed from a home, made headlines earlier this year as it was omitted from the new Oranga Tamariki Act as part of the overhaul of Child, Youth and Family (CYF). After a backlash, however, it was reinserted.

But when asked if the new research signalled issues with the policy, ministry boss Grainne Moss said it did not.

"The research says there's harm occurring, and there will be a number of factors contributing to that harm," she said. "What we then need to do is ask further questions around those contributors, and look at what actions we are taking to reduce them.

"We have done an international and domestic literature review which would indicate the transformation journey Oranga Tamariki is on is the right one, and actually we are addressing some of the contributing factors ...

"But all the report tells us is that harm is more prevalent than had been measured under previous definitions. We don't have enough numbers to make any conclusions [around placement types] that are statistically significant."

She said the ministry would be setting up an expert group to discuss the findings and propose a sustainable and robust future measurement and reporting approach.

New Zealand was "leading the way" in its "zero-tolerance" approach to harm, she said. In the past, New Zealand and international jurisdictions were under-reporting harm owing to narrow definitions of the word.

"The important thing for us is we have to know more to be able to do better.

"I think, for myself, and the leadership team, what this report does is strengthen our resolve to make sure we get this transformation journey right, and we do improve the quality of care of children in the system."

The ministry was established in April this year to replace CYF, after an expert panel proposed a series of major operations, design, and policy changes.

In 2013 to 2014, there were findings of substantiated abuse relating to 117 children in the custody of CYF, according to reports prepared by CYF for the Minister of Social Development.