The leader of Scotland's Catholic community has warned that moves by MSPs to legalise gay marriage will be "strenuously opposed" by the Church.
Keith O'Brien said any attempt to redefine marriage would be ‘strenuously opposed'.
Cardinal Keith O'Brien, in a strongly worded homily delivered at a mass for politicians in Edinburgh last night, claimed that allowing gay people to wed through a civil or religious ceremonies would be a "direct attack" on the institution of marriage.
However, the intervention sparked criticism from MSPs, with the openly gay leader of the Scottish Greens, Patrick Harvie, attacking the Cardinal's remarks as "absurd" and as an attempt to "suppress" the freedom of gays, lesbians and bisexuals.
The row came after the SNP government launched a 14-week consultation on allowing gay marriage - a change to the law that currently allows same-sex couples to enter a civil partnership, but bans the ceremony from church or other religious premises.
However, Cardinal O'Brien suggested that supporters of gay marriage wanted to "rewrite human nature" as he appealed to MSPs to oppose the proposed reform.
He said: "The Church esteems the institution of marriage as the most stable building block upon which any family can rest.
"The view of the Church is clear, no government can rewrite human nature; the family and marriage existed before the State and are built on the union between a man and woman.
"Any attempt to redefine marriage is a direct attack on a foundational building block of society and will be strenuously opposed."
There was also a sharply worded statement issued by the Bishops' Conference of Scotland yesterday, which suggested that the Scottish Government's consultation was "an exercise for justifying the campaign demands" of the "vociferous" gay rights lobby.
But Green MSP Mr Harvie attacked the Catholic Church's stance on gay rights and highlighted a Scottish Social Attitudes survey which revealed 60 per cent believe same-sex couples should have the right to marry.
"It's absurd to suggest that one marriage can undermine other marriages," he said.
"Just as non-Catholics respect Catholic marriages, so it's time for the Cardinal to start respecting the right of every adult to love who they please.
"The Cardinal should also remember that he doesn't speak for all people of faith, or even all Christians.
"There are many faith groups who want to conduct same-sex marriages for their members, and the Catholic Church seems determined to try and suppress their freedom to do so."
SNP MSP John Mason, who faced criticism for lodging a parliamentary motion that said no-one should be "forced" to approve of same-sex marriage, said he wanted "to encourage churches" to get involved in the debate about the proposals.
A Scottish Government spokeswoman said: "Our consultation, published last week, sets out that the Scottish Government tends towards the initial view that same-sex marriage should be introduced in Scotland but that faith groups and their celebrants should not be obliged to solemnise same sex marriages."