The CEO of Oranga Tamariki Grainne Moss has apologised for using Trade Me to advertise for foster carers and sharing details of children.
The agency says they have now taken the ad down and are now looking into the issue.
The Minister for Children Tracey Martin agreed it is "not the most appropriate website" to use.
However she said there is a strict screening process for foster carers.
The concerns were raised by National MP Alfred Ngaro.