For the first time Vatican officials will this week discuss in public sins committed by clergy considered so deadly that they require forgiveness from the Pope himself, including sexual abuse by priests and the profanation of Holy Communion wafers in Satanic rituals.

The Apostolic Penitentiary, currently headed by Cardinal James Stafford of the United States, the Major Penitentiary, was once described by Pope John XXIII as "the most secret" of Vatican departments. Starting tomorrow (Tuesday) however it will emerge from the shadows to hold a two day conference in Rome on the five "ultimate crimes" - abortion, using the Eucharistic host in Satanic rites, paedophile offences committed by the clergy, violation of the secrets of the confessional, and "offences against the person of the Pope".

The Apostolic Penitentiary, founded in the thirteenth century by Pope Honorius III (reigned 1216-1227) is a Vatican tribunal responsible for matters relating to confession, absolution, indulgences and the forgiveness of sins, and is sometimes described as "the tribunal of the soul". For the "five worst sins" however confession is not enough, and a special dispensation from the Pope himself is needed for absolution.

Bishop Gianfranco Girotti, Cardinal Stafford's deputy at the Penitentiary, said although he could not "give numbers", the five deadly sins were on the increase, and it took "constant work" by the tribunal to keep pace. In theory cases were decided at one sitting, but it sometimes took several sessions for the tribunal to satisfy itself that penance was "authentic, spontaneous and sincere", Monsignor Girotti said.

He said the conference was not an attempt to "showcase" the work of the Penitentiary but rather to "show that we are not a bureaucratic department but one of grace and mercy, charged by the Holy Father with giving life and meaning to confession, one of the most important of the sacraments. We deal with the ultimate goal of the Church - the salvation of souls".