The Catholic Church in Scotland has branded gay marriage a "dangerous social experiment" and dismissed homosexual relationships as nothing more than "friendships" as the SNP agreed to push ahead with same-sex unions.
Ministers in Edinburgh finally agreed the framework for legislation on Wednesday in a move described by some campaigners as a "proud day for Scotland".
But a spokesman for the Catholic Church in Scotland said: "The Scottish Government is embarking on a dangerous social experiment on a massive scale.
"The church looks much further than the short-term electoral time-scales of politicians.
"We strongly suspect that time will show the Church to have been completely correct in explaining that same-sex sexual relationships are detrimental to any love expressed within profound friendships.
"However, in the short term and long term the Church does not see same-sex marriage as an appropriate and helpful response to same-sex attraction."
The Catholic Church attracted criticism earlier on Wednesday as it emerged that the new Archbishop of Glasgow had suggested a young Labour MP, David Cairns, died because he was gay.
The Church's criticisms of gay marriage have grown in recent months in reaction to plans by the coalition in Westminster to bring in equal marriage.
In March the Church said "changing the legal definition of marriage would be a profoundly radical step."
"A change in the law would gradually and inevitably transform society's understanding of the purpose of marriage.
On Tuesday David Cameron said churches needed to "wake up" to the case for equality.
"[The] Church shouldn’t be locking out people who are gay, or are bisexual or are transgender from being full members of that Church, because many people with deeply held Christian views, are also gay," he said.
He told a reception for Lesbian, Gay, Bisexual and Transgender (LGBT) people last night:"And just as the Conservative Party, as an institution, made a mistake in locking people out so I think the Churches can be in danger of doing the same thing."
Equality campaigners in Scotland said the SNP's decision was "a proud day for Scotland".
Tom French, policy co-ordinator for the Equality Network, said Scottish Government had shown their determination to make Scotland "a more progressive country."
"With cross-party support for equality in the Scottish Parliament, we would expect that this change can be passed next year," he said.
"Same-sex marriage is about equality and freedom: the freedom for couples, and religious and humanist groups that want to, to celebrate same-sex marriages; but equally, upholding the freedom of other religious groups to say no to same-sex marriages."
"That's the right way for Scotland to deal with the different opinions on this.
While Colin Macfarlane, director of equality charity Stonewall Scotland, said: "Thousands of lesbian, gay, bisexual and transgender (LGBT) Scots and their families will be delighted with today's announcement. So will the majority of Scots who want our nation to be a beacon of respect and fairness.
"In recent months Scotland has been subject to a vitriolic campaign by some people who want to impose their 19th-century values on a 21st-century nation."
The arguments over gay marriage in Scotland have become increasingly bitter in recent weeks, with claims that opinion polls have been biased in favour of the opposing sides in the debate.
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