Child Youth & Family in Christchurch admits it has at times used security guards to supervise children in its care when a suitable placement cannot be found.
But the agency rejects claims from community agencies and school principals that the children are left alone inside a motel unit or other temporary accommodation with a security guard posted outside the door.
Te Mapua Trust says it has witnessed children under 12 being kept in hotel rooms with a security guard standing post - and in at least two cases there was no caregiver present for evenings or large periods of the day.
CYF southern regional director Chris Harvey told Nine to Noon the agency has used security guards in four instances in the past year - to keep children safe.
But he said the security guards were not in uniform and a support or social worker was present at all times.