Official figures show dozens of children have been abused when in the care of Child Youth and Family.
Social Development Minister Paula Bennett says she asked for the situation to be reviewed in 2010 when she learnt national data on children abused in CYF care wasn't being kept.
She confirms that review found 71 children had been abused.
"No abuse of children is tolerable or acceptable in this country. It is less than one percent. I would like it to be zero percent, but unfortunately in today's world that is not possible."
Green Party MP Holly Walker has demanded assurances of the Social Development Minister after official figures showed 71 children were abused in CYF care between July 2010 and June 2011.
"Can she assure the House that not one of them has suffered further abuse in care since."
Paula Bennett says 13 of the 71 cases resulted in court action, but the others, even though abuse was substantiated, weren't at a level where police could take a prosecution.
But she says she's been told all the children are now safe.