Pope Francis has told bishops around the world they must adhere to a policy of zero tolerance for clergy who sexually abuse children and begged forgiveness for ¡°a sin that shames us.

In a letter sent on Dec. 28 but released by the Vatican only on Monday, Francis said: ¡°I would like us to renew our complete commitment to ensuring that these atrocities will no longer take place in our midst.¡±

Since his election in 2013, Francis has taken some steps to root out sexual abuse in the Church and to put in place practices to protect children. But victims¡¯ groups say he has not done enough, particularly to hold to account bishops who tolerated sexual abuse or covered it up.