It is the first time that a Vatican official has been condemned for such a crime.

"There's something going on in the culture. And one of the elements of that cultural shift is that people are prepared to speak up in a way that they would never have done before."

The report is expected to reveal details of widespread abuse and efforts to conceal and protect abusive priests.

An increase in calls to dioceses to report claims of clergy sexual abuse has happened before, and is likely to happen again in the wake of the credible claim lodged against Cardinal Theodore E. McCarrick, retired archbishop of Washington, according to the head of the U.S. bishops' Secretariat for Child and Youth Protection.

The retired archbishop of Washington said he will no longer exercise any public ministry "in obedience" to the Vatican after an allegation he abused a teenager almost 50 years ago has been found credible.

Oscar Karadima revealed that he was among the group of priests and laypeople who met with Pope Francis on June 2 and spoke to him about the suffering his family endured, following the revelation that his brother was found guilty of sexual abuse.