Imams in Glasgow have told all Muslims throughout Scotland not to vote for any local election candidate on 3 May who supports redefining marriage.
The news will trouble the leaders of major parties, all of whom have indicated their personal support for the plan.
A statement was issued yesterday by the Council of Glasgow Imams and it is being sent out to Muslims throughout Scotland.
The statement said: “We urge the Deputy First Minister Nicola Sturgeon to look very seriously at this fundamentally important issue and to re-consider the full implications of what she is proposing.
“We wish to inform both her and the First Minister Alex Salmond that we are deeply unhappy and vigorously opposed to the proposed legislation for same sex marriage.
It added: “We will be urging our community from the pulpit to make sure that any person they consider voting for does not favour the proposed legislation.”
The Scottish Government, controlled by the Scottish National Party, is currently analysing over 50,000 responses to its public consultation on redefining marriage.
When the consultation was launched the SNP-led Scottish Government said it “tends towards the view” that marriage should be redefined, but would listen to all views before making a final decision.
The SNP is hoping to gain control of Glasgow City Council, but that will be more difficult if the city’s Muslims decide not to support its candidates because of its stance on gay marriage.
The Church of Scotland and the Roman Catholic Church in Scotland have also expressed their opposition to changing the definition of marriage.
And a petition against the plan, organised by campaign group Scotland for Marriage, has been signed by over 18,000 people.
A Scottish Government spokesman said: “The consultation on same-sex marriage and registration of civil partnerships has now closed and we are now analysing the responses and considering what next steps to take.
“As was made clear when the consultation was launched, while we have expressed our initial view, we have given an assurance that all opinions will be listened to, no final views have been reached and therefore no decisions have been taken. The analysis of the responses will be published later in the spring.”