Retired Pope Benedict XVI has published an analysis on the Catholic Church's clergy sex abuse scandal, blaming it on the sexual revolution of the 1960s and church laws that protected priests.

The essay immediately raised eyebrows, seeming to interfere with or even contradict Pope Francis' own efforts to confront one of the most critical issues facing the church.

One church historian called Benedict's essay "catastrophically irresponsible," because it conflicted with Francis' own efforts to lead the church out of the sex abuse crisis.

Benedict in 2013 had said he planned to retire to a lifetime of penance and prayer and would leave Francis to guide the church.

U.S. church analysts said the essay, published in the German monthly Klerusblatt, was both flawed in content and problematic on universal church level, exacerbating existing divisions in the church that have emerged between supporters of Francis and Catholics nostalgic for Benedict's doctrine-minded papacy.

In his introduction, Benedict said both the Vatican secretary of state and Francis had given him permission to publish it. The Vatican press office confirmed it was written by Benedict.

In the essay, Benedict traced the start of the clergy abuse crisis to the sexual revolution of the 1960s, citing the appearance of sex in films in his native Bavaria. He also blamed the crisis on failures of moral theology in that era, as well as church laws that gave undue protection to accused priests.

Benedict wrote that during the 1980s and 1990s, "the right to a defense (for priests) was so broad as to make a conviction nearly impossible."

As Cardinal Joseph Ratzinger, Benedict reformed those laws in 2001 to make it easier to remove priests who abused children. Benedict took a hard line against clerical sex abuse as the Vatican's conservative doctrine chief, and later as pope, defrocking hundreds of priests accused of raping and molesting children.

"Why did pedophilia reach such proportions? Ultimately, the reason is the absence of God," he wrote.

Francis has blamed the scandal on a clerical culture in the church that raises priests above the laity.

Villanova University theologian Massimo Faggioli said the essay was thin in its analysis by effectively attributing the scandal to the sexual revolution. He said it omitted key cases, such as the Legion of Christ founder's pedophilia, which began well before then.

"If a pope emeritus decides to stay silent, it's one thing and can be defended. But speaking and telling a tiny part and a very personal version of the story, it's hard to defend," he said on twitter.

"Everything we know in the global history of the Catholic abuse crisis makes Benedict XVI's take published yesterday very thin or worse: a caricature of what happened during in the Catholic Church during the post-Vatican II period - with all its ingenuities and some tragic mistakes," he tweeted.

Church historian Christopher Bellitto questioned if Benedict, who turns 92 next week, was being manipulated by others. He said the essay undermined Francis' own efforts to steer the church out of the crisis.

Bellitto said the essay omitted the critical conclusions that arose from the pope's February sex abuse summit in Rome, including that "abusers were priests along the ideological spectrum, that the abuse predated the 1960s, that it is a global and not simply Western problem, that homosexuality is not the issue in pedophilia."

"It is catastrophically irresponsible, because it creates a counter-narrative to how Francis is trying to move ahead based on the 2019 summit," he said. "The essay essentially ignores what we learned there."

David Gibson at Fordham University's Center on Religion and Culture agreed with that assessment.

"For a retired pope to try to undo the critical work of a sitting pope and on such a crucial issue seems ... bad," he said.