Girls as young as 18 months who came into contact with the NSW child welfare authorities from the 1930s onwards were routinely tested for venereal disease and evidence of sexual activity.

If they were found, on the basis of a spurious vaginal examination, to have been sexually active, from the age of 10 upwards they could be sent to the Parramatta Girls Home where they were exposed to ''state-sanctioned rape'' perpetrated by doctors, supervising staff and other inmates.

The notorious detention centre for girls, which shut down after public outcry in 1974, is the focus of hearings for the Royal Commission on Institutional Responses to Child Sexual Abuse starting on Wednesday.