German Jesuit Fr. Hans Zollner left the Vatican's Pontifical Commission for the Protection of Minors, established by Pope Francis in 2014.
In a statement, he explains there was a lack of transparency in the Commission's work.
Fr. Zollner says there was no clarity in the process of selecting staff members, the definition of their roles and the commission's financial accountability. He states that the relationship between the Commission and the Dicastery for the Doctrine of the Faith was not clearly outlined.
He also describes the internal communication as poor, saying members often received insufficient and vague information about how and why decisions were made.
The Jesuit priest states he will continue to work with the Institute of Anthropology at the Pontifical Gregorian University and with the diocese of Rome as an advisor.
Fr. Zollner has been one of the Vatican's most public faces in the fight against abuse under Pope Francis.