A leading Vatican cardinal said on Thursday the Roman Catholic Church will never bless gay marriage, wading into a controversy over the issue in Italy and other countries.

On Tuesday, Italian Interior Minister Angelino Alfano ordered mayors to stop recognizing the validity of gay marriages performed outside the country, prompting protests from rights groups and local officials.

"We have to be honest," Cardinal Francesco Coccopalmerio, the Vatican's highest ranking expert on Church law, said on Thursday when asked if he could foresee the Church ever granting "some sort of blessing" for gay couples.

"For us, and not just for us but for human culture in general, marriage is between a man and a woman," he told a briefing on a synod, or assembly, of some 200 Roman Catholic bishops discussing family matters.

The cardinal said the Church did not judge homosexual couples, regarding them as people of good faith.

"But to bless this type of union ... to say that they are like (heterosexual) marriages, never. This is simply for reasons of logic and identity. To bless them is not part of the way we see Christian doctrine," he said.