A Bill to redefine marriage has been published by the Government, but critics call it “an appalling piece of legislation”.
MPs will get their first chance to debate and vote on the Bill on Tuesday 5 February.
Opposition to the plan has been spearheaded by the Coalition for Marriage (C4M) group, backed by 630,000 British people.
C4M campaign director Colin Hart said: “The Marriage (Same Sex Couples) Bill which has been published today by the Government is an appalling piece of legislation.
“It creates two divisive and unequal forms of marriage and fails to deal with the important questions about how to protect those who work in the public sector, especially teachers who we learn today could face being disciplined or sacked for backing traditional marriage.
“No wonder the former Home Secretary David Blunkett described the policy as ‘a complete dogs dinner’ and former Defence Secretary Liam Fox said it was ‘divisive’ and ‘ill-thought through’.
“The current definition of marriage is backed by 70 per cent of the public. Even within the gay community less than 40 per cent see this as a priority, while less than one in five (19 per cent) trust the PM’s motives.
“For months David Cameron and Nick Clegg have been saying that their proposals are strictly limited to marriage and will not have any negative effect. But the Bill published today finally puts a sword to this lie.
“It is time the Government postpones or drops this bill before they marginalise hundreds of thousands of ordinary people and wreck the institution of marriage.”
Earlier today, a senior source close to Education Secretary Michael Gove admitted that the Government may be powerless to stop teachers getting fired for their beliefs about marriage.
And The Times reported that David Cameron is struggling to convince a majority of his own MPs to support the Bill.
David Cameron’s own mother, when asked why her son is alienating so many Tory voters, said: “I know, but David just won’t be told.”
Announcing the Bill, equalities minister Maria Miller said: “I believe that couples should not be excluded from marriage just because they love someone of the same sex.
“In opening up marriage to same-sex couples, we will further strengthen the importance of marriage in our society.”