ROME — The Catholic Church’s child sexual abuse scandal ensnared one of Pope Francis’s top lieutenants on Thursday, underlining the halting progress the reformist pontiff has made in addressing decades of abuse by the clergy even as Cardinal George Pell declared himself innocent of the charges against him.

Pell, one of the most powerful officials in the Vatican, said he would return to his native Australia to fight multiple charges of sexual assault. He became the highest-ranking Vatican official to be formally accused by law enforcement when Australian police charged him earlier Thursday.

Advocates for victims of child abuse said that allowing Pell to face charges in Australia, rather than keeping him inside the Vatican City’s walls, was already a major step for a church that might have shielded him in earlier years. But they also said that the cardinal’s ability to remain in his post until Thursday, despite controversy about his role in the Australian church’s years of abuse, was a sign that Francis had not fully reckoned with one of the most painful chapters in modern Catholic history.

The case pulls Francis’s papacy back into the abuse scandals that have battered the church for nearly two decades and led to demands for sweeping changes on monitoring, selecting and training the clergy. In the United States and elsewhere, groups continue to press for full accountability within the Catholic Church for alleged abuse of children and others going back generations. Many recommendations of a flagship reform commission empaneled by Francis, meanwhile, have been endorsed by the pope, then ignored by the Vatican bureaucracy.

Speaking to reporters in the Vatican, a subdued Pell denounced “relentless character assassination” in the media.

“I repeat that I am innocent of these charges. They are false. The whole idea of sexual abuse is abhorrent to me,” said the 76-year-old cardinal, who until Thursday was in charge of reforming the church’s antiquated and opaque finances.

Pell, Australia’s most senior Catholic prelate, has faced questions for years about his role in the Australian church’s staggering scale of sexual abuse. But he had never been directly charged.

Australian officials did not offer details of the alleged crimes, saying that Pell has a right to due process as they charged him with multiple counts of “historical sexual assault offense.”

He is scheduled to appear before a Melbourne court on July 18.

The Vatican, meanwhile, said it had learned of the charges “with regret” and that Francis appreciated the cardinal’s honesty and commitment during his three years in the Holy See.

Spokesman Greg Burke noted in the statement to reporters that Pell has “repeatedly condemned as immoral and intolerable” acts of abuse against minors.

Francis has a mixed record on dealing with abuse, according to survivors and their advocates. He has done far more than his predecessors to try to prevent further crimes, but some critics say they are disappointed that he has sometimes appeared reluctant to punish priests for past abuses.

“The pope certainly does understand the effects of abuse, the horrible damage it does to victims, and he has made an effort. But on the other hand, we haven’t seen an enormous amount of change,” said Marie Collins, an Irish survivor of clergy sexual abuse who quit Francis’s commission in March because she was frustrated that few reforms were taking hold.

“I was more hopeful a few years ago than I was now, because I’ve seen close up how difficult it is to get change,” Collins said. “It can’t all be laid at the feet of Pope Francis.”

Defenders of Francis say he has held priests accountable, including as recently as last month, when he defrocked, or ejected from the priesthood, an Italian man, Mauro Inzoli, who was convicted of child sex abuse in an Italian court. The decision was announced Wednesday.

Still, perhaps emblematic of Francis’s record, the decision came only after he had reversed a previous move by Pope Benedict XVI to defrock the priest.

Pell’s decision to face charges in Australia was seen as another positive signal by some Vatican-watchers.

“These facts pertain to abuses that have been too long underestimated by the church’s mentality, and it’s only fair that they should not be downplayed,” said Andrea Tornielli, a Vatican journalist who has also co-written a book with Francis.

The papal commission’s work has also been moving forward, if slowly. One current member said she felt pleased about the recommendations the panel has made on the training of priests and the treatment of abuse victims.

“I am optimistic. Perhaps I am wrong. But I came to the commission with hope that we will be able to learn lessons from historical survivors and then to improve the protection of minors every day,” said Catherine Bonnet, a French psychiatrist.