The Holy See’s judicial arm said there was a risk that criminals would misuse confidential information intended for the eyes of a confessor only.

It did not say if the warning had been prompted by an actual case of blackmail. No figures have been released for the number of confessions heard online. The Vatican has embraced the internet with enthusiasm, and since 1997 has had an efficient website powered by computers named after the archangels Michael, Gabriel and Raphael and run by nuns.

The Pope, while warning of the “dark uses” to which the internet can be put and the “temptations” it offers, has used it to send messages and prayers around the world. However, he is against group confessions and collective absolutions.

Last April, in an apostolic letter entitled Misericordia Dei, he declared that group confession had to be “a rare response to grave necessity”, not a routine form of the sacrament.

Vatican officials said that although collective absolution had become popular in parts of the Catholic world, it was an exceptional measure to be used when the normal celebration of the sacrament is physically or morally impossible.

Some Catholic dioceses have set up their own computer networks to spread the faith and offer spiritual support and advice. In Canada, the Archdiocese of Winnipeg established a network two years ago so that online visitors could talk to priests in chat rooms or seek “virtual prayer guidance” from nuns.

After the Vatican website was set up, the Italian Catholic magazine Famiglia Cristiana warned readers to beware of “flirting” through chat rooms, declaring that that amounted to “online adultery”.

“For Christians there is no moral difference between a virtual affair and a flesh-and-blood betrayal,” the magazine said. “The internet cannot wash your sins away.”

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