A Vatican symposium on the priesthood, including discussions on sexual abuse, was embarrassed on Friday by the discovery that a French priest disciplined for alleged sexual abuse was among the attendees, witnesses said.

The priest was Father Tony Anatrella, 81, who was barred from public ministry in France in 2018 after a Church investigation found that he abused adult seminarians he was treating in so-called conversion therapy aimed at suppressing their homosexuality.

The Vatican declined to comment, but a Church source confirmed Anatrella's presence after it was first reported by the French Catholic newspaper La Croix.

Anatrella was seen at the symposium by the La Croix reporter as well as a reporter for the French Catholic news agency I Media, one of whom spoke to him.

Anatrella, 81, could not be immediately reached and it was not immediately clear if he was still at the symposium on Friday afternoon after news of his presence had broken. The three-day event began on Thursday.

Anatrella, a psychotherapist who had previously advised the French Church and the Vatican, denied wrongdoing at the time he was disciplined by the French Church.

La Croix said one of its reporters saw Anatrella's name on the list of participants and that the priest had lunch on Thursday along with other participants in the restaurant of the Santa Martha residence where Pope Francis lives.

The Vatican source said only the speakers were invited by the Congregation of Bishops, which sponsored the symposium, and those who attended registered though an outside events organising company.    

The conference is discussing, among topics, the effects of the sexual abuse crisis on vocations to the Roman Catholic priesthood.

Anatrella registered as a priest for the Vatican event. The French Church in 2018 banned him from public ministry but did not defrock him. 

"It is perplexing that despite his personal history, which caused immense pain to a number of people, the priest can still move around normally, without limits," said an editorial on Il Sismografo website, which specialises in Church affairs and also separately reported Anatrella's presence. 

"The Vatican has some problems in its communications with the French episcopate," the editorial said.

Pope Francis did not mention the sexual abuse crisis when he opened the symposium on Thursday.

Cardinal Marc Ouellet, the head of the Congregation for Bishops, said in his opening address that it was taking place "in the current historical context dominated by the drama of sexual abuse by priests".