A woman whose marriage to a bishop became a major scandal in the 1960s is calling on Pope Francis to make priestly celibacy optional, according to a report by the Associated Press.

Clelia Luro, who is also a friend of the newly elected pope, is convinced that he will eventually lead the global church to end mandatory priestly celibacy, a requirement she says "the world no longer understands".

She believes this could resolve a global shortage of priests, and persuade many Catholics who are no longer practicing to recommit themselves to the church.

"I think that in time priestly celibacy will become optional," Luro said in an interview with The Associated Press in her home in Buenos Aires, after sending an open letter to the pope stating her case. "I'm sure that Francis will suggest it."

John Paul II, Benedict XVI and other popes before them forbade any open discussion of changing the celibacy rule, and Francis hasn't mentioned the topic since becoming pope last month.

"I don't see how in any way this would form part of his agenda," said the Rev. Robert Gahl, an Opus Dei moral theologian at the Pontifical Holy Cross University in Rome.

But as Cardinal Jorge Mario Bergoglio, he referred to the issue of celibacy in ways that have inspired advocates to think that the time for a change has come.

In his book "On Heaven and Earth," published last year, Bergoglio said: "For the moment I'm in favor of maintaining celibacy, with its pros and cons, because there have been 10 centuries of good experiences rather than failures." But he also noted that "it's a question of discipline, not of faith. It could change," and said the Eastern Rite Catholic church, which makes celibacy optional, has good priests as well.

Luro and her husband, the former bishop of Avellaneda, Jeronimo Podesta, felt ostracised from the church for many years, but she says Bergoglio didn't hesitate to minister to them when Podesta was hospitalised before his death in 2000. They became such good friends thereafter that Luro said Bergoglio called her every Sunday for 12 years, and often discussed the celibacy issue as they debated all sorts of hot topics in private conversations.