A leading Roman Catholic journalist has said he is concerned that laws protecting gay and lesbian people from discrimination could lead to prison for some clergy.

John L Allen is an expert commentator on Vatican affairs for CNN and is known for his objectivity.

He has published two books about the current Pope.

Writing in his regular column in the National Catholic Reporter he said the recent decision of the British government not to grant exemptions for Catholic-run adoption agencies from new rules outlawing discrimination is leading to a criminalisation of belief.

Mr Allen called the gay rights movement an “irresistible force” and predicted more clashes with Christians who think that the model of the traditional family is under threat.

Pope Benedict has denounced civil partnerships and gay marriage as an affront to Catholic ideas about marriage.

“The love of a man and a woman is at the origin of the human family and the couple formed by a man and a woman has its foundations in God’s original plan,” Benedict said in a message to young people released today.

“It’s not much of a stretch,” Mr Allen wrote, “to imagine pastors being fined or even imprisoned for statements opposing the rights of homosexuals to marry or adopt.”

In September last year Stephen Green, director of Christian Voice, was arrested at the Cardiff Mardi Gras for leafleting.

Mr Green was approached by officers who asked him to stop leafleting people, but he was arrested when he continued to distribute leaflets with extracts taken from the Gospel.

In a statement Mr Green claims: “I thank God for the honour of being locked up for sharing the Gospel of Jesus Christ.”

Roman Catholic prelates threatened to close their adoption agencies rather than consider gay and lesbian couples as adoptive parents, but now appear to have accepted that they will not be able to refuse people on the grounds of their sexuality.

The government have granted Catholic adoption agencies a grace period until the end of 2008 to adjust to the new anti-discrimination laws, which are due to come into force in April.