Children's Commissioner Andrew Becroft says the number of children being harmed in state care is "deeply disturbing and utterly unacceptable".
More than 220 children who were removed from their families to keep them safe went on to be harmed in state care over a six-month period.
The Oranga Tamariki findings were the first from the new reporting system on child harm.
In the worst cases, children had been raped or beaten. Several incidents led to criminal charges.
Andrew Becroft told Mike Hosking this situation is "non-negotiable wrong".
"Any way you cut it, obviously it is deeply disturbing, utterly unacceptable. You can't take kids from their own home for abuse and then have them abused again."
However, he said it was not a reflection that Oranga Tamariki is failing.
"This is a courageous step. Publishing the extent of the problem, as known to the department...we have never had this before and I don't know of any other agency in the world, that's committed itself to being so transparent."
"It sets a benchmark but clearly we have to do better."
The Children's Commissioner said being a caregiver comes with added stresses that other parents don't deal with.
"It's a stressful and challenging job with kids who come from some of the most damaging environments ever."
He said caregivers need more support, education and assistance while caring for children.
The new system is one of broadest and most detailed in any jurisdiction. It records abuse committed against a child by anyone, not just the caregiver, and in any location, not just within the child's placement. It records all incidents of harm, accidental and intentional, and ranging from over-zealous discipline of a child through to severe physical or sexual assaults.
As of June last year, there were 6350 children and young people in state care in New Zealand. Between July and September, 130 of them were found to have been harmed. Between October and December, 97 were found to be been harmed.
Some of the incidents were historical but were first reported during this period. A few children were harmed more than once. They were mostly likely to have been abused by caregivers, though many of the sexual assaults were committed by other young people or unrelated adults.
How to get help
If you're in danger now:
• Phone the police on 111 or ask neighbours of friends to ring for you.
• Run outside and head for where there are other people.
• Scream for help so that your neighbours can hear you.
• If you are being abused, remember it's not your fault. Violence is never okay.
Where to go for help or more information:
• NZ Police
• The Harbour, for those affected by harmful sexual behaviour
• Help Auckland 24/7 helpline 09 623 1700
• Rape Prevention Education
• Wellington Help 24/7 crisisline 04 801 6655, push 0
• Male Survivors of Sexual Abuse
• Women's Refuge: Free national crisis line operates 24/7 - 0800 REFUGE or 0800 733 843 www.womensrefuge.org.nz
• Shine, free national helpline 9am- 11pm every day - 0508 744 633 www.2shine.org.nz
• Shakti: Providing specialist cultural services for African, Asian and Middle Eastern women and their children. Crisis line 24/7 0800 742 584
• White Ribbon: Aiming to eliminate men's violence towards women, focusing this year on sexual violence and the issue of consent. www.whiteribbon.org.nz