Bishops from 100 countries and the leaders of 33 religious orders will take part in the four-day meeting, as well as the Vatican's anti-paedophilia prosecutor Charles Scicluna and one abuse victim, Ireland's Marie Collins.

Pope Benedict XVI is expected to issue a special blessing for the conference at the Vatican's Gregorian University, which will also launch a Centre for Child Protection in Germany to fight sex abuse by the clergy in the church worldwide.

The symposium entitled ``Towards Healing and Renewal'' will include a service in which representatives of seven religious orders which had paedophile clergy in their midst will plead for forgiveness.

Victims' groups have criticised the event.

``You can have all the symposiums you want but why don't you open a constructive debate. The church is too closed,'' said Roberto Mirabile, of the Italian victim support group La Caramella Buona.