Cardinal Sean Brady has voiced vehement opposition to Irish government plans to criminalise priests who do not report sex abuse admitted in the confessional.

Speaking for the first time on the issue yesterday, the Archbishop of Armagh embarked on a collision course with Taoiseach, Enda Kenny, when he insisted that any intrusion on the sacraments was "a challenge to the very basis of a free society".

Under the legislation, currently being drawn up, a priest would be guilty of a criminal offence if they were told of a sexual abuse case and failed to report it to the civil authorities.

This has been viewed as an assault on the Vatican's canon law, which stipulates: "The sacramental seal is inviolable; thus it is absolutely illegitimate for the confessor to make the penitent known, even only in part, using words or any other means, and for any reason."

The Catholic Primate described confession as "a sacred and precious rite" and he insisted that any intrusion on the sacrament was "a challenge to the very basis of a free society." In an address to several thousand pilgrims at Knock Shrine, Co Mayo, the cardinal said freedom to participate in worship and to enjoy the long-established rites of the church were fundamental rights.

Without referring directly to the proposal, he said: "For example, the inviolability of the seal of confession is so fundamental to the very nature of the sacrament that any proposal which undermines that inviolability is a challenge to the rights of every Catholic to freedom of religion and conscience."

Last night, a spokeswoman for the Republic's Department of Justice said minister Alan Shatter "reiterates his statement" that the Criminal Justice (Withholding Information on Crimes against Children and Vulnerable Adults) Bill will apply regardless of any internal rules of any religious grouping.