Notorious paedophile priest Gerald Ridsdale will spend at least another three years in prison after being sentenced for sexually abusing another 12 children while working in the Catholic Diocese of Ballarat.

Ridsdale, 83, will now spend a total of 33 years in prison for what County Court Judge Irene Lawson described as unprecedented and grave offending over 30 years.

"Throughout the period from 1961 to 1988 whilst an ordained priest you committed sexual offences against 65 children on a more or less continuous basis," she said.

"Your appalling pattern of offending was quickly established following your ordination.

"You knew at all times what you were doing was wrong, you exploited the children's naivety."

The court heard Ridsdale's offending had no boundaries, with some of the children assaulted inside the confessional box or on the altar.

One of his victims was abused at a church in Ballarat from the age of eight.

Judge Lawson said the "startling aspect" to that case was that the victim's father would take the child to Ridsdale to be abused.

On one occasion the child was taken from their bed, had their clothes removed in the confessional box and was carried to the altar to be assaulted by the paedophile priest.

Judge Lawson said Ridsdale had abused his position of trust and power to access children for his own sexual gratification.

"You were a revered priest and trusted by devout Catholic families who respected you," she said.

"You have caused very serious consequences to each individual victim.

"Their childhoods have been blighted and their later lives affected."

Ridsdale sat with his head in his hands as his depraved history of offending was read to the court.

He has been in prison serving concurrent sentences since 1994.

Ridsdale will now be eligible for parole in 2022, an additional three years on his previous earliest release date of 2019.

Judge Lawson said it was "increasingly likely" Ridsdale would die in jail.