Legalising same-sex marriage would damage the fabric of society, the Archbishop of Canterbury, Justin Welby, has warned.  

It is the first time Archbishop Welby, the head of the Church of England and the Anglican Communion world wide, has intervened in the debate, the Daily Telegraph reports.

It comes ahead of today’s vote in the House of Lords on the Coalition Government’s same-sex marriage Bill, where observers suggest the vote will be very close.

The Archbishop, who sits in the House, has said he cannot support the Bill in its current form.

Speaking on the first day of debate on the Bill in the House of Lords, the Archbishop warned that legalising same sex marriages would be a social problem, not a faith issue

“We think that traditional marriage is a cornerstone of society,” he told peers.

“Rather than adding a new and valued institution alongside it for same gender relationships, which I would personally strongly support to strengthen us all, this Bill weakens what exists and replaces it with a less good option that is neither equal nor effective,” he said.

“The concept of marriage as a normative place for procreation is lost; the idea as marriage as covenant is diminished; the family in its normal sense, predating the state, and as our base community of society, as we have already heard, is weakened.

“It is not at heart a faith issue,” he said. “It is about the general social good. So with much regret but entire conviction I cannot support the Bill as it stands.”  

The Archbishop criticised the Bill for mistakenly treating marriages and weddings as the same thing. Gay couples can have equality without needing to be able to marry, he said. “Two things may be equal but different.”

The Bill also fails to deliver equal rights for homosexuals because it distinguishes clearly between same-sex and opposite-sex marriage, “thus not achieving true equality”.

“The result is confusion. Marriage is abolished, redefined, and recreated, being different and unequal for different categories.”

The new definition of marriage is “an awkward shape” with same-sex and opposite sex marriages “scrunched into it” but not fitting well, the Archbishop said.

He warned that the reform “weakened” the concept of the “normal” family as the basis for a strong community and replaced traditional marriage with something “less good”.

The Lords debate follows a vote in favour of the Marriage (same sex couples) BIll in the Commons last month. The issue has split the Conservative party down the middle.

Lord Dear, a former chief constable, urged peers to reject the “ill-considered” Bill. He warned that it risked inflaming hatred of homosexuals and was a “moral minefield”.

“We find ourselves in a world where an ill-conceived Bill seeks to overturn centuries of tradition, heedless of public opinion and religious leaders and blind to the laws of unintended consequences,” he said.

However, the government warned that the future of marriage as an institution depended on opening it up to modern society.

Baroness Stowell of Beeston said: “I am speaking in support of those same-sex couples who want the opportunity to marry because very simply this government considers their love and commitment to be no different from that of opposite sex couples.

“We believe same-sex couples should be able to marry if they want to and extending that choice is the right thing to do for them and the right thing to do for the future of marriage,” she said. If marriage is to continue to flourish, “we need the institution to reflect our modern inclusive society”.