Cardinal Donald Wuerl, archbishop of Washington, speaks during a news conference at the Cathedral of St. Matthew the Apostle in Washington. File picture: Susan Walsh/AP Photo.

VATICAN CITY - The archbishop of Washington D.C. stepped down over the handling of sex abuse cases but received fulsome praise from the pope, drawing criticism from campaigners who said it showed the Catholic Church cared more for its leaders than abuse victims.

Cardinal Donald Wuerl, a loyal ally of Pope Francis, was criticised in a U.S. grand jury report in August for failing to halt abuse in his previous role as archbishop of Pittsburgh.

He becomes one of the highest ranking Catholic leaders to step aside over global accusations that the Church harboured sex abusers. His resignation also further exposes a rift between Francis and members of the Church's conservative wing, some of whom say the pope himself should quit over the sex abuse crisis.

In a glowing letter of support, Francis made clear that he accepted Wuerl's resignation reluctantly, at Wuerl's insistence, and believed he was not guilty of trying to conceal abuse. "You have sufficient elements to 'justify' your actions and distinguish between what it means to cover up crimes or not to deal with problems, and to commit some mistakes. However, your nobility has led you not to choose this way of defence. Of this, I am proud and thank you," the pope wrote.

Victims advocacy groups were outraged.

"The pope’s letter to Cardinal Wuerl sends a clear message that for Pope Francis, Cardinal Wuerl is more important than the children he put in harm’s way," said Terence McKiernan, president of BishopAccountability.org.

"Until Pope Francis reverses this emphasis on coddling the hierarchy at the expense of children, the Catholic Church will never emerge from this crisis," he said in a statement.

Wuerl has come under fire since the release in August of a U.S. Grand Jury report on sexual abuse which found evidence that at least 1,000 people, mostly children, had been sexually abused by some 300 clergymen over the course of 70 years.

The report covered six diocese in Pennsylvania, including Pittsburgh, where Wuerl served as archbishop from 1998-2006. The report mentioned Wuerl's name more than 200 times. Wuerl has defended his overall record in Pittsburgh.

In a highly unusual move, Francis asked Wuerl, who keeps the title of cardinal, to stay on as administrator of the Washington diocese until another archbishop could be appointed. Usually a new bishop is announced at the same time as such a resignation.

The Washington position is the most important and visible for the Church in the United States because of its proximity to national political power.

"Francis would want to take his time in finding a successor in sympathy with his vision of where the Church should be going," said Father Tom Reese, author of several books on the Vatican and the Roman Catholic Church in the United States.

ERRORS IN JUDGMENT

In a statement thanking the Pope, Wuerl said he apologised for "any past errors in judgment".

"My resignation is one way to express my great and abiding love for you, the people of the Church of Washington," he said.

The Church has recently been hit by one sexual abuse scandal after another, from Germany, to the United States, to Chile. At the same time, a deepening polarisation between conservatives and liberals in the Church has played out on social media.

In his letter to Wuerl, the pope said he recognised that Wuerl wanted to step down for the greater good of the Church. He also thanked Wuerl for "actions that support, stimulate and make the unity and mission of the Church grow above every kind of sterile division sown by the father of lies."

In Christian parlance, "father of lies" is a synonym for the devil. Francis has said the devil is ultimately behind sex abuse of children by priests and current divisions in the Church.

Wuerl has also been accused of knowing that his predecessor in Washington, ex-cardinal Theodore McCarrick, had forced male adult seminarians to have sex with him years ago. Wuerl denies having been aware.

In July McCarrick became the first cardinal in about 100 years to be stripped of his red hat and title of "eminence".

Francis ordered McCarrick to retire to a life of prayer and penitence after American Church officials said as part of a separate investigation that allegations that McCarrick had sexually abused a 16-year-old boy almost 50 years ago were credible and substantiated.

Francis has sought to make the Church more welcoming to divorced Catholics and homosexuals, and has chosen to concentrate on social issues such as poverty and immigration rather than moral ones. But that has angered conservatives, some of whom have accused him of heresy and sowing confusion among the faithful.