A Catholic bishop has warned the Government that legalising same-sex marriage would change the meaning of marriage itself.

In what will be seen as an opening move in Catholic Church opposition to the same-sex marriage referendum next spring, Bishop Kevin Doran said it would mean “the unique relationship between marriage and procreation would disappear completely from the definition of marriage”.

“Since this is probably the principal reason for the State to have any interest in regulating marriage ... why bother regulating it at all?” Bishop Doran said. “One might even ask, why in that case would the State restrict marriage to two people? What, in the final analysis, is the difference between a ‘sexual friendship’ (in which the State has no interest) and a marriage?”

Gay lifestyle

He said “societies rely on families built on strong marriages to produce what they need but cannot secure: healthy upright children who become conscientious citizens.

“As they mature, children benefit from the love and care of both mother and father, and from their parents’ committed and exclusive love for each other. Unlike friendships, which vary in kind and degree and formality, marriage ... has enough objective structure, apart from the spouses’ preferences, to be legally regulated.”

Dr Doran, Bishop of Elphin since last July, was delivering a talk on “Marriage and the Common Good” in Roscommon town, organised by the Iona Institute think tank.