By Alex Stevenson
Conservative MPs preparing to defy their leader over gay marriage are being told their career prospects are under threat, ahead of tomorrow's vote.
Backbenchers have been handed a free vote in the marriage (same sex couples) bill, which is debated in the Commons for the first time on Tuesday.
But the absence of the whips does not mean the issue is being ignored, as media attention focuses on the Conservative parliamentary party's views on the issue.
The coalition government's legislation putting same-sex marriage on an equal legal footing with heterosexual couples has prompted massive opposition, led by religious groups.
Despite the bill containing a 'quadruple lock' which the government claims will protect organisations like the Church of England from legal challenge, incoming Archbishop of Canterbury Justin Welby is expected to speak out against the legislation later.
Only around 120 Tory MPs are expected to vote with coalition ministers in tomorrow's second reading bill, with around 60 set to abstain.
Some Cabinet ministers may even vote against the proposal, including defence secretary Philip Hammond, environment secretary Owen Paterson and Welsh secretary David Jones.
Opponents of the bill including Tory backbencher David Burrowes will welcome a report from the ResPublica thinktank at an event in parliament later.
It argues marriage is "inescapably heterosexual" as its primary purpose is to provide a form of social insurance for children and their mothers.
"It cannot be reduced to a contract between the partners, since it is the way in which one generation makes way for and cares for its successor," co-author Professor Roger Scruton argued.
"More than any other institution, society depends on marriage for its future, and no government should meddle with marriage without having the most serious of reasons - reasons far more serious than those so far given."
Writing in the Times newspaper, however, culture secretary Maria Miller acknowledged her party found "easy accord" hard to achieve on the issue.
But she insisted the Conservatives would make "challenging decisions" and "govern in that vein".
"If a couple love each other, then the state should not stop them getting married unless there is good reason — and being gay is not reason enough," she wrote.
"For some individuals and faiths, that statement goes beyond their beliefs and that has to be respected. It is not the role of government to tell people what to believe. However, the state does have a responsibility to treat people fairly."
The controversy may not prove quite the vote-loser for the Tories some in the party are warning. Only seven per cent of voters believe the issue will be decisive in affecting how they vote at the next general election, a poll by YouGov found.