An Irish priest who has been threatened with excommunication from the Catholic Church has said there was a link between clerical sex abuse and mandatory celibacy.

Tony Flannery, who has been warned about his outspokenness by the Vatican before, said that the celibate lifestyles that priests were forced to live led to a struggle over sexuality and could, in some cases, result in children being sexually abused.

He was preparing to launch his book, A Question of Conscience, which questions the Vatican watchdog, the Congregation for the Doctrine of the Faith (CDF), in the methods it uses to "stamp out" anything it regards as dissent.

Flannery was a founding member of the Association of Catholic Priests in Ireland. In February 2012, the CDF became unhappy with some of his writings relating to the Church and he was summoned to Rome, where he was ordered to step down as ACP leader.

Months later, the CDF ordered him to issue a statement saying that he believed women could never be ordained as priests and that he accepted all the moral teachings of the Church. He was suspended from ministry and threatened him with excommunication.

In his book, Flannery has published all the documentation from the CDF relating to his case.

In an interview with the Irish Independent ahead of the book launch, the 66-year-old said priests faced an "inevitable" struggle with their sexuality.

Problem will not go away

"The Catholic Church in Ireland seems to believe that it has dealt with the problems of clerical sexual abuse by putting structures in place to protect children," he said.

"Nobody within the official church has looked at the deeper issues and seriously asked the question why so many priests did these things because it raises fundamental questions about the lifestyle of priests.

"Can they say with any degree of definiteness that the fact that so many priests abused children is not connected to celibacy and clericalism and the whole style of life that a priest is forced to live?

"I don't think they can and until such time as the church authorities face up to that and seriously discuss it and investigate it, the problem will not go away."

Flannery said priests were forced to live in isolation and lacked real human interaction. The led some to "turn to children for sexual outlets", he maintained.

The sex abuse scandal in the Catholic Church in Ireland began in the 1990s as a series of criminal cases, which established that thousands of children had been the victims of hundreds of paedophile priests.

In March 2010, the Pope apologised to victims.