A leading Catholic cardinal and key adviser to Pope Francis has called for the Vatican to "swiftly and decisively" adopt strict policies for cases of sexual abuse involving bishops and top clergy.

Cardinal Sean O'Malley of Boston issued the appeal with the Church in the United States still reeling from allegations that another cardinal was involved in abuse of minors and sexual improprieties with adult seminarians years ago.

Cardinal O'Malley said he was "deeply troubled" by the case of Cardinal Theodore McCarrick and that it and others "raise up the fact that when charges are brought regarding a bishop or a cardinal, a major gap still exists in the Church's policies on sexual conduct and sexual abuse".

The statement also comes as the Vatican has been hit by a major scandal that has engulfed the Church in Chile.

Last month, the Vatican ordered Cardinal McCarrick, 88, the retired archbishop of Washington DC, to cease public ministry after finding that allegations he sexually abused a teenager almost 50 years ago were credible.

The revelation stunned American Catholics because Cardinal McCarrick was one of the US Church's most respected leaders, particularly when he was archbishop of the US capital from 2000 to 2006 and was a confidant of popes and presidents.

Since then, several men have come forward to allege that Cardinal McCarrick had forced them to sleep with him at a beach house in New Jersey when they were adult seminarians studying for the priesthood.

He has said he has "absolutely no recollection" of the alleged abuse of the minor but has not commented on the allegations of abuse of adult men.

The New York Times reported last week that two dioceses in New Jersey had reached financial settlements in 2005 and 2007 with men who said they were abused by him as adults decades ago.

"The Church needs a strong and comprehensive policy to address bishop’s violations of the vows of celibacy in cases of the criminal abuse of minors and in cases involving adults," Cardinal O'Malley said.

In 2015, the Vatican announced plans for a special tribunal to judge bishops in sexual abuse cases. But it never got off the ground because of legal and bureaucratic problems.

Cardinal O'Malley appeared to suggest that the tribunal be revived; saying accusations against bishops and cardinals required a "fair and rapid adjudication".

"Failure to take these actions will threaten and endanger the already weakened moral authority of the Church"

A widening scandal involving accountability of bishops for sexual abuse has buffeted the Catholic Church in Chile.

In May, all of Chile's 34 bishops offered to resign after a meeting with the pope over allegations of a cover-up of sexual abuse. Pope Francis has so far accepted five resignations and is expected to accept more.

In a major development in that scandal, the Church in Santiago said the Chilean public prosecutor's office had summoned the capital's archbishop to testify in an investigation into the alleged cover-up.