THE Catholic Church will today intensify pressure on Alex Salmond over same-sex marriage by calling for a referendum on the proposals, before the First Minister's flagship independence vote.

The leader of Scotland's Catholics, Cardinal Keith O'Brien, has warned the First Minister that "far more people" are concerned about same-sex ceremonies than independence.

A spokesman for the Church told The Herald it wanted a public vote on the issue before a referendum on independence.

Ministers are expected to announce proposals for gay marriage after a Cabinet meeting tomorrow. They are under intense pressure from opponents, including campaign groups and churches. More than 27,000 people have signed a petition against the plans.

However, the First Minister is facing calls from many within his own party to press ahead with the proposals. At the weekend Jim Eadie, the SNP Edinburgh Southern MSP, said: "The message to the Scottish Government should be: 'Stand firm, hold your nerve.'"

Muslim leaders and the Catholic Church have denounced the plans and accused Scottish ministers of offering "worthless" assurances over opt-outs.

Cardinal O'Brien, who has previously described the proposals as madness, specifically linked gay marriage and independence in a statement last night calling for a referendum.

He pointed out that almost 80,000 people responded to an official consultation on same-sex marriage while 26,000 have responded to the one on independence.

Cardinal O'Brien said: "The Scottish Government's consultation on redefining marriage had three times more respondents than the consultation on the constitution, demonstrating clearly that far more people are concerned about fundamental matters of morality at the present time.

"Clearly, if it is sensible to hold a referendum on independence, it is crucial we have one on marriage. It is the only way the country can move forward on this issue. Let all those who have a view on this subject place their trust in the Scottish people and let Scotland decide."

John Deighan, parliamentary officer for the Catholic Church in Scotland, said the vote on same-sex marriage should take precedence. "We would like to see it before the independence referendum," he said. "From what we can see, this seems to be a higher priority for many people".

A spokeswoman for the Scottish Government would not be drawn on the potential for a referendum on gay marriage.

However, Colin Macfarlane, director of Stonewall Scotland, said: "The Cardinal's last-ditch call for a referendum is desperate and totally out of step with public opinion. Stonewall Scotland's latest poll, carried out by Yougov, found two-thirds of Scots supported same-sex marriage. MSPs were elected on clear manifesto commitments to consult on equal marriage and decide on the evidence, and that is what they should do. A referendum would therefore be totally undemocratic and a huge waste of taxpayers' money."

Tim Hopkins, director of the Equality Network, said: "We are confident the majority of people in Scotland support same-sex marriage but policy in Scotland is not decided by a referendum.

"We allocate our government to weigh up all the evidence and take decisions and we are confident it will do that effectively."

Last week, an opinion poll demonstrated that Scottish ministers might lose such a public vote if one were held on same-sex marriage. The figures suggested just more than half of Scots opposed the proposals.

The Catholic Church argues marriage should only be between a man and a woman. It has also warned churches and priests could face court action if they refused to allow same-sex ceremonies in their places of worship.

The Church also says it believes responses to the Scottish Government's consultation ran at roughly two-to-one against.

Cardinal O'Brien has authorised a plan to raise £100,000 for a campaign against same-sex marriage. The Church plans to hold a "support marriage Sunday" at the end of next month, just before MSPs return to Holyrood from their summer break.

More than 27,000 people have signed a petition – organised by Scotland for Marriage, an umbrella group supported by the Catholic Bishops' Conference of Scotland – against the plans.

When it announced the consultation, which closed in December, the Scottish Government said it tended towards the view same-sex marriage should be introduced. However, it said faith groups would not be obliged to take part in ceremonies.

The Scottish Government spokeswoman said: "The Cabinet has had a first discussion on the next steps following the consultation on same-sex marriage and the registration of civil partnerships and has asked for some further detail. We fully expect to be in a position to publish the way ahead this month."