A man laid his naked daughter on a church altar where paedophile priest Gerald Francis Ridsdale sexually assaulted her, a court has heard.

Australia’s worst paedophile priest has admitted sexually abusing another 12 children, one as young as six, over three decades.

Ridsdale told some of his victims the abuse was “part of God’s work”, the Victorian county court heard on Tuesday.

On one occasion in 1974 a father woke his scared young daughter to take her to a Catholic church in Ballarat where Ridsdale abused her.

“[The 10-year-old’s] father carried her to the confessional booth and took her clothes off her, then carried her to the altar and lay her down,” crown prosecutor Jeremy McWilliams said.

Ridsdale then indecently assaulted her.

“Ridsdale told her: ‘Jesus died for our sins so we could be forgiven and if I confess to this sin I might be forgiven.’

“Then he kissed her on the cheek.”

Ridsdale told a nine-year-old altar boy “God will forgive all of your sins” as he raped him, McWilliams said.

Afterwards he told the sobbing boy to pray for forgiveness.

“He also told [him] that if he ever told anyone, God would punish his family.”

The man said he had been warned by other boys at the Mortlake Catholic school not to get caught alone with Ridsdale, but had no idea why until he was himself abused.

“I am in my 36th year of a sentence for a crime I did not commit,” the man told the court. “My sentence is for life.”

Judge Irene Lawson broke down as she told the man that as a nine-year-old he was in no way responsible for what happened.

Ridsdale used his position as a parish priest to befriend the children and their devout Catholic families in towns in western Victoria. He told some of his victims “it’s our little secret”.

McWilliams said Ridsdale told one boy: “Don’t tell your mum and dad or your dad could die.”

Ridsdale pleaded guilty to 23 charges, mainly indecent assaults but including rape, for abusing 11 boys and one girl between 1962 and 1988.

The former priest has already been convicted for sexually abusing 53 children, although his true number of victims is believed to be in the hundreds.

Defence counsel Tim Marsh said Ridsdale fainted after a fall on his way to court on Tuesday, but the 83-year-old insisted on being there for his plea hearing.