The Vatican said Pope Francis has accepted the resignation of a U.S. bishop convicted for failing to report a priest who collected lewd photographs of minor children.

Bishop Robert Finn stepped down Tuesday as head of the Diocese of Kansas City-St. Joseph, Missouri in the Midwestern U.S.

Finn is the highest-ranking Catholic official in the United States to be convicted in connection with a suspected case of child abuse involving a member of the clergy.

The Vatican did not give a specific reason for Finn's resignation but said the pontiff accepted it under canon law.

Prosecutors said the diocese did not notify police for six months after pornographic pictures of young girls were discovered on the computer of the Reverend Shawn Ratigan in 2011. 

Bishop Finn was convicted in 2012 of failure to report suspected child abuse and sentenced to two years' probation but retained his post.

Activist groups who support victims of sexual abuse at the hands of Catholic clergy urged Francis to dismiss Finn.

Anne Barrett Doyle, the co-director of BishopAccountability.org, an online abuse resource group, said in a statement that Finn's resignation a "a good step but just a beginning," and called on the pontiff to publicly state that he removed Finn for failing to protect children.

"The pope must show that this decision represents a meaningful shift in papal practice, that it shows a new era in bishop accountability," Barrett Doyle said. "That would be unprecedented, and it would send a bracing message to bishops and religious superiors worldwide that a new era has begun."

Francis is also under pressure to remove Bishop Juan Barros of Chile, who is accused of shielding the Reverend Fernando Karadima, a notorious pedophile priest.

The Vatican convicted the now 84-year-old Karadima of child abuse in 2011, and ordered him to retire to a “life of prayer and penitence.”