The harm caused by Australia's worst pedophile priest Gerald Francis Ridsdale is still being felt, a victims' advocate says.

The former Victorian Catholic priest has admitted to abusing more than 60 children, but the true number could be as high as 1000.

Ridsdale, 82, today pleaded guilty to 20 new charges including rape, buggery and indecent assault against another 11 victims between 1962 to 1988.

"I plead guilty to all charges as presented," Ridsdale told the Melbourne Magistrates' Court.

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He will now face a two-day plea hearing on August 15 before being sentenced.

"Yes, I understand. Thank you, Your Honour," he told the court.

The latest charges relate to 10 boys and one girl in Ballarat and the surrounding area.

Ridsdale has already been convicted of abusing 53 children between 1961 - the year he was ordained - and the late 1980s.

Ridsdale was a skilful and devious predator who may have sexually abused as many as 1000 children, victims' advocacy group Broken Rites spokesman Dr Wayne Chamley said.

"It's not just the 60 or so that he's been charged with. It's in the hundreds," Chamley told AAP.

"He was starting to abuse children when he was still a seminarian and he continued it until he was in his 60s."

Ridsdale abused children throughout the Diocese of Ballarat, which covers the western third of Victoria, and after being sent to work in Sydney in the 1980s.

"For the people of western Victoria it's been one of the great tragedies, just a horrendous impact on the lives of hundreds of people, families, siblings," Chamley said.

Two Ballarat bishops knew of Ridsdale's crimes, one as early as his first year as a priest. And two Sydney archbishops knew he had "sexual problems" and should be kept away from children, the child sexual abuse royal commission has previously heard.

"The lives of children were not as important as the reputation of the Catholic Church," Chamley said.

Former Ballarat Bishop Ronald Mulkearns, who died last year, knew in 1975 that Ridsdale had abused boys but moved him between parishes where he continued offending.

"The combination of Mulkearns' alcoholism and Ridsdale's pedophilia was a total disaster for children from Ballarat to Portland," Chamely said.

"We're still living with the fallout."

Ridsdale spent three months in prison after his first convictions in 1993 and has been in jail since 1994, serving an effective total sentence of 28 years.

- AAP

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