Pope Francis said on Sunday he would not respond to explosive accusations by a former top Vatican official that the pontiff had covered up sexual abuse, saying dismissively that the document containing the allegations "speaks for itself."

Francis, talking to reporters aboard the plane returning to Rome from Dublin, said he would "not say one word" on the 11-page document, in which the former official says Francis should resign. The pontiff said journalists should read the document carefully and decide for themselves about its credibility.

Archbishop Carlo Maria Vigano, the former Vatican ambassador to Washington, accused the Pope on Sunday of having known of allegations of sex abuse by a prominent U.S. cardinal for years. The accusations, published by the National Catholic Register and several other conservative media outlets in the United States and Italy, was an unprecedented broadside against the Pope by a Church insider.

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"I read that statement this morning. I read it and I will say sincerely that I must say this, to you [the reporter] and all of you who are interested: read the document carefully and judge it for yourselves," Francis said.

"I will not say one word on this. I think the statement speaks for itself and you have sufficient journalistic capacity to reach your own conclusions," he said.

Archbishop alleges coverups

In remarkably blunt language, Vigano said alleged coverups in the church were making it look like "a conspiracy of silence not so dissimilar from the one that prevails in the mafia."

"Pope Francis has repeatedly asked for total transparency in the Church," wrote Vigano, who has criticized the Pope before.

Pope Francis must be the first to set a good example for cardinals and bishops who covered up McCarrick's abuses and resign along with all of them. - Archbishop Carlo Maria Vigano

"In this extremely dramatic moment for the universal Church, he must acknowledge his mistakes and, in keeping with the proclaimed principle of zero tolerance, Pope Francis must be the first to set a good example for cardinals and bishops who covered up McCarrick's abuses and resign along with all of them," he said.

Informed Vatican on McCarrick in 2006

Vigano said he had told Francis about the accusations against McCarrick in June 2013, just after he was elected Pope by his fellow cardinals.

Vigano, the papal envoy in Washington from 2011 to 2016, also said he had informed top Vatican officials as early as 2006 that McCarrick was suspected of abusing adult seminarians while he was a bishop in two New Jersey dioceses between 1981 and 2001.

He said he never received a response to his 2006 memo.

Ex-cardinal Theodore McCarrick, right, resigned from the Church in July after a review concluded that claims he had sexually abused a 16-year-old boy were credible. (Jonathan Newton/The Washington Post/Associated Press)

He also accused McCarrick's successor as archbishop of Washington, Cardinal Donald Wuerl, of having been aware of the abuse allegations. Wuerl has said he did not know of them.

The statement was the latest blow to the credibility of the U.S. church. Nearly two weeks ago, a grand jury in Pennsylvania released the findings of the largest-ever investigation of sex abuse in the U.S. Catholic Church, finding that 301 priests in the state had sexually abused minors over the past 70 years.

Historic resignation

McCarrick in July became the first cardinal in living memory to resign his position in the church leadership after a review concluded that claims he had sexually abused a 16-year-old boy were credible.

He was one of the highest-ranking church officials accused of sex abuse in a scandal that has rocked the 1.2 billion-member faith since reports of priests abusing children and bishops covering up for them were reported by the Boston Globe in 2002.

Since then, patterns of widespread abuse of children have been reported across the United States and Europe, in Chile and Australia, undercutting the Church's moral authority and taking a toll on its membership and coffers.

Protesters calling attention to clerical sex abuse march to the Garden of Remembrance , timed to coincide with the Papal Mass at Phoenix Park on Sunday. (Aaron Chown/Associated Press)

McCarrick, 88, has said he had no recollection of alleged abuse of the minor but has not commented on widespread media reports that he would force adult men studying for the priesthood to sleep with him at a beach house in New Jersey.

Vigano's statement railed against "homosexual networks present in the Church" — the word "homosexual" appears 18 times, while the word "child" appears only twice, in both cases in the titles of Church documents Vigano cites.

Francis asked for forgiveness on Sunday during his highly charged visit to Ireland for the "scandal and betrayal" felt by victims of sexual exploitation by Catholic clergy.

With files from The Associated Press