Victoria's child safety watchdog has raised concerns over the dangers of temporary agency staff caring for young people after a boy was abandoned in a park at night.

Police and the Department of Human Services are investigating two social workers after they abandoned the nine-year-old when he refused to leave after a group outing.

They have been stood down pending the results of the investigations but their supervisor, who reportedly instructed them to leave the boy, has not.

Child Safety Commissioner Bernie Geary said he would look into the case if requested by Community Services Minister Mary Wooldridge.

"It seems to be an appalling case of negligence," he told AAP on Thursday.