Speaking at a press conference metres from the walls of the Vatican City, the head of the Survivors Network of those Abused by Priests (SNAP) said his group had made a formal submission to the UN Committee on the Rights of the Child.

"It's a long submission of 30 pages based on government reports by five different nations," David Clohessy told reporters, surrounded by photographs of children he said were members of his organisation, at the age they were abused.

"We hope that the UN speaks out very forcefully and says that the Vatican is in violation of the treaty that it agreed to honour."

The SNAP submission argues that the Holy See has violated the UN Convention on the Rights of the Child, which it signed in 1990, on four counts including a failure to cooperate with criminal investigations and failing to protect children.

The crisis over the abuse of children by clergy, which has bankrupted several US dioceses, cost the Church billions in compensation claims worldwide and haunted it throughout Benedict's papacy, has returned as cardinals prepare to enter a conclave to elect the next pontiff.