In joint letter to 'The Sunday Telegraph', the imams quote the Quran and say they are fulfilling a "sacred trust to God" by airing their views and accuse the UK government of attacking "the cornerstone of family life".
"The Muslim community will take this issue very, very seriously because now the Government has interfered with family. To us that is like taking children away from their mother: it will definitely have an effect on Mr Cameron's vote.
The letter is published as British MPs prepare for their final House of Commons debate on the government's Same-Sex Marriage Bill.
It echoes comments by Anglican and Roman Catholic clergy, who have also described marriage as a "sacred contract between a man and a woman" which they say "cannot be redefined".
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Gay couples in the UK already have the right to enter into civil partnerships but supporters of same-sex marriage argue that separate civil partnerships perpetuate the notion that same-sex relationships are not as valid as heterosexual ones and that legal rights are still not exactly the same as those conferred by marriage.
Under the Same-Sex Marriage Bill, the Church of England and the Church in Wales will be banned from offering same-sex marriages because of their strongly stated opposition, unless they change canon law.
There are currently no plans for similar legislation in Northern Ireland, but there are already plans for a bill to allow same-sex marriage in Scotland.