Activists fighting for truth and justice for victims of sexual abuse by Catholic priests hold out little hope for progress under the next pope as controversy brews over a US cardinal who covered up for predator clerics.

A Catholic association has asked retired Los Angeles archbishop Roger Mahony to stay away from next month's conclave after he was stripped of all public duties for mishandling claims against dozens of priests.

Campaigners say the disgraced cardinal's behaviour is precisely what Pope Benedict XVI has failed to crack down on and point to other "cardinal electors" linked to abuse scandals that have rocked the Catholic Church in recent years.

"He should have the good sense to stay well away from Rome," said Roberto Mirabile, director of the Italian anti-abuse group La Caramella Buona, whose lobbying helped convict a paedophile parish priest near Rome last year.

Supporters reject the demonisation of Benedict on this issue and say he has been the first pontiff to really confront the problem, meet with victims and punish abusers, as well as try to formulate Church-wide rules against abuse.

"The atmosphere has really changed in the Church over abuse of minors during his pontificate," said Marco Scarpati, Italy director for Ecpat, an international organisation against child prostitution, pornography and trafficking.

"The Vatican has taken in claims, opened quite in-depth investigations and acted with a severe hand against convicted priests," he said.

But victims groups say that is far from enough given the scale of the problem.

"We're not in the least bit optimistic," said Sue Cox of the Britain-based Survivors Network Europe, herself a victim of a paedophile priest when she was 10-13 years of age.

"They would prefer for it all to go away," she told AFP, voicing her fear that "with all the pomp and ceremony they will try to bury the past."

The scourge of abusive priests burst into the light of day more than a decade ago with a cascade of scandals rocking the Church worldwide, from Ireland to the United States, from Australia to the pope's native Germany.

The Vatican says it continues to receive around 600 claims against abusive priests every year, many of them dating back to the 1960s, 1970s and 1980s.

Barbara Dorris of the Survivors Network of those Abused by Priests, or SNAP, in the United States said the tide of revelations cannot be turned back. "Criminal cases are breaking all over," she said. "The floodgates are opening."

Cox and other activists say the conclave includes several cardinal electors who are implicated directly or indirectly in the scourge.

Chief among them is Mahony, who was archbishop of Los Angeles from 1985 to 2011 and appeared to systematically protect abusers from criminal prosecution, according to hundreds of documents released by the investigation.

An online poll carried out by Italian Catholic weekly Famiglia Cristiana found an overwhelming majority of respondents were against Mahony.

-- If eradication means firing all implicated bishops, 'so be it' --

Another US cardinal who is expected to attend the March conclave, Justin Francis Rigali, resigned as Philadelphia archbishop for age reasons.

But activists say the resignation was in fact linked to a wide-ranging scandal in the city involving 37 priests for which an underling took the fall.

Another of the 117 cardinal electors who can vote on a new pope is Belgian Godfried Danneels, who had computer files seized at his home three years ago over suspicion that he may have helped cover up hundreds of abuse cases.

Irish cardinal Sean Brady has faced resignation calls from campaigners for allegedly failing to stop a serial abuser, saying he was not senior enough when he took part in a Church investigation of the priest in the 1970s.

The Vatican has taken a number of recent initiatives, including an unprecedented conference at the Gregorian University in Rome last year which brought together victims, bishops from around the world and psychologists.

The Vatican in 2011 also called on bishops' conferences around the world to come up with guidelines on how to deal with abuse, but not all countries have responded and there is concern that countless abuses remain hidden.

"Benedict XVI was very courageous in breaking the wall of silence that covered many cases," said Maltese bishop Charles Scicluna, formerly the Vatican's chief prosecutor against abuses.

Victims groups have made demands that sound radical for a 2,000-year-old institution known for its secrecy and rigid hierarchy.

SNAP says the Vatican could publish the names of predatory priests on the Internet or order bishops to report all cases of sexual abuse to the police.

Robert Hoatson, head of the US group Road to Recovery, says if eradicating abuse "means firing all the bishops that have covered up, so be it.