Rome, Italy (CNN) -- Pope Benedict XVI said Friday the church must promise "to do everything possible" to ensure that the sexual abuse of children by Catholic priests "will never occur again."
He was addressing thousands of priests who had gathered at the Vatican for a three-day conference to mark the end of the "Year of the Priest."
"So it happened that, in this very year of joy for the sacrament of the priesthood, the sins of priests came to light -- particularly the abuse of the little ones, in which the priesthood, whose task is to manifest God's concern for our good, turns into its very opposite," the pope said.
Pope Benedict XVI said the church must "insistently beg forgiveness from God" and from victims for the sexual abuse committed by Catholic priests. He also said priests must be more thoroughly vetted before joining the ministry.
"In admitting men to priestly ministry and in their formation, we will do everything we can to weigh the authenticity of their vocation and make every effort to accompany priests along their journey, so that the Lord will protect them and watch over them in troubled situations and amid life's dangers," the pope said in his homily.
Some victims of sexual abuse said the pope's words weren't enough.
"Forgiveness comes after, not during, a crisis," said Barbara Blaine, president of the U.S.-based Survivor Network of those Abused by Priests (SNAP), "Right now, kids are being assaulted by priests and bishops are concealing the crimes. And the pope continues taking no action to stop this."
She said the pope still ignores the main problem, "the ongoing recklessness, deceit, and callousness of bishops who, even now, protect predators instead of children."
The pope's promise to "do everything possible" is a vague pledge that won't change the behavior of abusive priests, Blaine said.
She called for independent investigations into the extent of cover-ups wherever the abuse occurred, and criminal prosecution of abusive priests and their colleagues and supervisors.
Thousands of people have come forward in the United States, Ireland, the Netherlands, Austria and the pope's native Germany, saying they were abused as children by Catholic clergy.
The crisis has particularly shocked deeply Catholic Ireland, where three government-backed investigations have uncovered physical and sexual abuse stretching back decades.
The pope referred to "currents which lead the flock astray" in his homily Friday.
"Today, we can see that it has nothing to do with love when conduct unworthy of the priestly life is tolerated," he said.
Critics charge that the Vatican systematically covered up abuse around the world by shuffling abusive priests from one parish to another or quietly pushing them to retire.
The pope has met with victims in the United States and in Malta, and vowed that the church will seek justice for the victims.
But some victims say justice is not enough, and that the priesthood must be reformed.
Tuesday, activists campaigned for the Catholic Church to ordain women. They argued that women in the priesthood could have helped lessen the impact of the child abuse scandal sweeping the church.
"We believe that if women had a say in the church, if there was more accountability and more transparency, that the men would have been held more accountable," said Erin Saiz Hanna, executive director of the U.S.-based Women's Ordination Conference.