An Australian ex-priest convicted of sexually abusing children had another 12 months added to his 39-year prison sentence on Tuesday for molesting a 72nd victim.

Gerald Ridsdale, 89, has been in prison since 1994 for a series of convictions for abusing children between 1961 and 1988 while he worked as a Roman Catholic priest in churches and schools across his home state of Victoria.

He was sentenced in the Ballarat Magistrates Court to an additional year after he pleaded guilty in June to indecently assaulting a 13-year-old boy while he worked at a Catholic school in Horsham in 1987.

It was his 193rd conviction for child abuse.