Two former nuns said Wednesday that a world-renowned artist priest made them take part in threesomes and watch porn so they would "grow spiritually".

Slovenian mosaic artist Marko Rupnik, 69, is accused of sexually and psychologically abusing at least 20 women for nearly 30 years at a religious community in Slovenia.

"He took me to pornographic theatres to help me 'grow spiritually'," Gloria Branciani, who was a member of the community until 1994, told journalists at a press conference in Rome.

"He said that I would not grow spiritually if I did not meet his sexual needs," she said, describing how he sexualised religious concepts.

"We had another nun have sex with us because he said it was like the Trinity," Branciani said, referring to the central Christian doctrine of three persons within one God.

Rupnik was briefly excommunicated in 2020 for absolving someone of having sexual relations with him, but was reinstated after he formally repented.

He was finally expelled from the Jesuit order -- of which Pope Francis is a member -- last June.

In October, Francis waived the statute of limitations on the offences, opening the way for potential disciplinary proceedings.

Anne Barrett Doyle, co-director of the abuse tracking site Bishop Accountability, which documents abuse within the Catholic Church, described Rupnik as a "powerful cleric who was protected at the highest levels of the Church and the Vatican."

The press conference comes five years after an unprecedented summit at the Vatican on sexual abuse in the Church, at the end of which Francis promised a "zero tolerance" approached.

"The Rupnik case shows that little has changed," said Barrett Doyle, who called for an independent investigation and the publication of its findings.