Prosecutors in Argentina have issued an international arrest warrant for Bishop Gustavo Zanchetta, who is accused of sexually abusing young trainee priests, known as seminarians. He denies the charges.
Bishop Zanchetta, 55, who is close to his fellow Argentine Pope Francis, lives in the Vatican.
He reportedly resides in Casa Santa Marta, an accommodation block in the shadow of St Peter's Basilica where Francis has lived ever since his election six years ago.
Argentinian prosecutors have complained that the bishop has failed to respond to repeated emails and telephone calls about the abuse allegations, which were made last year by two young seminarians. The trainee priests also accused him of mismanagement of the diocese's finances and abuse of power.
If convicted, the bishop would face up to 10 years in prison, but there is no extradition treaty between Argentina and the Vatican and for now he seems to be safely ensconced in Rome.
The stand-off emerged as Pope Francis made an impassioned speech in Bangkok on behalf of victims of sex trafficking, prompting accusations of a double standard in the Catholic Church's stance on sex crimes.
"Despite being suspended from ministry, the Vatican has argued that Zanchetta's 'daily work' requires him to be in Rome instead of facing trial in Argentina. This decision is at best questionable and at worst a Vatican-sponsored opportunity for Zanchetta to flee from justice," said Zach Hiner, the executive director of victims' pressure group SNAP, the Survivors Network of those Abused by Priests.
"If Pope Francis was serious about his "all-out battle" against cases of clergy abuse, he would order Zanchetta to return to Argentina and face the allegations against him."
Anne Barrett Doyle, of BishopAccountability.org, which documents the abuse crisis in the Catholic Church, said: "It's vital that Pope Francis ensures Zanchetta's full cooperation with Argentine civil authorities. To do otherwise would put the Pope in violation of his own decree forbidding conduct by bishops that interferes with civil investigations.
"Francis must begin to set an example - especially because his protectiveness toward Zanchetta to date already raises disturbing questions about his commitment to ending complicity by Church officials.
"Francis should not have given Zanchetta safe harbour in the first place, given the bishop's reported wrongdoing in Argentina."
In a Mexican television interview earlier this year, the Pope said he had asked Zanchetta about the accusations, which involved nude selfies on the bishop's mobile phone.
Francis said he gave his friend the benefit of the doubt after he claimed his phone had been hacked.
A representative for the bishop in Rome insisted that Zanchetta had always cooperated with investigators.
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