The figure comes from the Ministry for Children's own public reporting on abuse in care, which it has been publishing since 2019.
Oranga Tamariki has been under-fire after Newsroom published a leaked video showing a young person being tackled, restrained and held in a headlock by staff at the ministry's care and protection unit in Christchurch.
Since then, an investigation has been launched, staff at the facility have been stood down and it has been decided the residence, Te Oranga, would close.
Oranga Tamariki's Safety of Children in Care reports have shown there have been numerous instances where staff have physically harmed children, including in residences.
Oranga Tamariki was initially releasing the Safety of Children in Care reports quarterly, but that has since reduced to biannual reporting.
Several of the reports, which are available on the ministry's website, said most of physical harm caused by staff involved "escalated behaviour" and often happened during restraint procedures.
In the report for the March 2019 quarter, Oranga Tamariki said the majority of physical harm caused by staff within its residences and other group home settings was related to discipline or behaviour management.
"Harm often occurred during restraint procedures but was not accidental and involved the use of excessive physical force," the report said.
In the latest biannual report, for the six months to December 2020, there were 13 findings of physical harm against children where staff were responsible.
In that report and others, Oranga Tamariki said, in cases where harm was caused by staff, an assessment of any ongoing risks was undertaken and "appropriate actions taken".
Oranga Tamariki has previously told RNZ it has taken immediate disciplinary action against staff who have been found to have harmed children.
RNZ has sought further details from Oranga Tamariki about the action taken, including whether any staff have lost their jobs or been referred to police, but the ministry said those questions would have to be processed as an Official Information Act request.
In a statement, Oranga Tamariki said the senior leadership team is provided with the reports and acting chief executive Sir Wira Gardiner has been briefed on the findings of the previous reports.
"Publicly releasing the data in these reports is important and we need to be open and transparent about the issues involved," the ministry said.
"We know the children and young people who come into our care often have complex needs and managing those needs safely - sometimes in challenging circumstances with high risks present - is difficult.
"We are continually looking for ways to improve our practice. The Safety of Children in Care reports help us do this."
Children's Commissioner Judge Andrew Becroft said Oranga Tamariki has been well aware of the issue of staff physically harming children for some time.
But he said there needed to be greater transparency about what happened once the ministry was notified of an incident.
In high-level cases where the police are called in, Becroft said he was confident there would be a thorough and independent investigation into what happened.
However, lower-level cases would be dealt with by Oranga Tamariki itself.
Becroft said any incidents where staff have physically harmed children should be reported to an external monitoring authority, which would then have the power to follow up what steps were taken.
The Office of the Children's Commission has a statutory role to monitor Oranga Tamariki residences.
Becroft said his office has kept its regular monitoring reports and recommendations to the ministry confidential, but he was now pushing for that to change.
"We felt we tried to play by the rules, but it hasn't worked. I think it's obvious that our reports now need to be public and released every time we write one.
"We are in the midst of renegotiating our memorandum of understanding with Oranga Tamariki and it will change."
The Safety of Children in Care reports showed that Oranga Tamariki staff were not the only people abusing children in care.
All up, in the six months to December 2020, there were almost 300 instances of neglect, or emotional, sexual or physical abuse, affecting more than 200 children.
The abusers also included caregivers, parents, other children and adult family members.
