One of the highest ranking Catholics in the US has been asked to stop all public ministry after the Vatican found he was credibly accused of sexually abusing a teenage boy almost 50 years ago. 

Cardinal Theodore McCarrick, the former archbishop of Washington, DC, is now retired. He insists he is innocent after he was accused of commiting abuse while a priest in New York. But an investigation by the Church found the allegations to be credible and substantiated, the archdiocese said in a statement.

McCarrick is one of the most senior of more than 6,700 US Roman Catholic clerics to be accused of sexually abusing children since the church's sex abuse scandal broke in 2002, according to BishopAccountability.org, a private group that tracks the allegations.

'The Vatican Secretary of State, Cardinal Pietro Parolin, at the direction of our Holy Father, Pope Francis, has instructed Cardinal McCarrick that he is to refrain from any public ministry or activity until a definite decision is made,' the archdiocese said. McCarrick said he would follow the Vatican's instruction.

'While I have absolutely no recollection of this reported abuse, and believe in my innocence, I am sorry for the pain the person who brought the charges has gone through,' McCarrick said in a statement.

The clergy sex abuse scandal erupted in Boston and rippled around the globe as abuse was found in many countries, costing the church billions of dollars in settlements and undercutting its moral authority.

Pope Francis has worked to address the scandal, meeting twice with victims of clergy sex abuse. He came under heavy criticism in January, when he vigorously defended Chile's Bishop Juan Barros, who was accused of witnessing a priest's abuse of boys and doing nothing to stop it.

After returning to the Vatican, the pope sent an investigator to speak to victims and witnesses, and accepted three Chilean bishops' resignations, including that of Barros. In an interview with Reuters, he said he may accept additional bishops' resignations.

In addition to the priests accused of sexually assaulting children, high-powered leaders including former Boston's Archbishop Cardinal Bernard Law were accused of allowing accused priests to continue to minister to children. Law died in December.

'This is an absolutely stunning revelation... The fact that the Church itself is finding it is credible and substantiated suggests that it indeed is because the Church does not say that lightly,' said Anne Barrett Doyle, a board member at BishopAccountability.org.

Additional reporting from Reuters.