Social Development Minister Paula Bennett says family members must speak up if they know a child is being placed in the care of someone inappropriate.
Child Youth and Family have apologised to a Taranaki woman who, after a family group conference, was placed in the care of her uncle, a convicted rapist, in 2001.
The rules changed this year, and police checks are now made on all family conference placements.
In Parliament on Tuesday, Ms Bennett said there were nine family members at that conference, and extended families have a role to play in providing checks and balances.
The Minister says mandatory police checks are now done on all family group conference placements.
Asked whether police checks would be made on placements made before the rule change, Ms Bennett said she would have to seek advice about the resources needed to do that.
The Green Party says the Minister should put the cost aside and investigate, as children placed in care as recently as December last year, could be in danger.