In the spotlight: Labour and Lib Dem MPs voting against gay marriage

Away from the Conservative civil war on gay marriage, a handful of supposedly liberal MPs are having their own crisis of conscience.

Two Liberal Democrat MPs plan to vote against the bill to legalise equal marriage later, despite the fact their own Lynne Featherstone is responsible for pushing it forward as equalities minister.

One of them is Gordon Birtwhistle, MP for Burnley. His take is simple: "Civil partnerships are fine. Gay marriage is just not on."

The second is John Pugh, from Southport, whose argument is rather more nuanced (and impenetrable).

"The current proposals endeavour to equate homosexual partnerships which are in principle non-child bearing with heterosexual partnerships which are in principle procreative and establish a set of rules for state supported sexual relationships that are blind to sexual orientation," he said in a blog post. "They demonstrably fail to achieve the objective set."

There are another nine Lib Dem MPs who are listed on the Coalition for Equal Marriage website as not declaring for or against. They are: Alan Beith, Annette Brooke, Duncan Hames, John Hemming, Charles Kennedy, Greg Mulholland, Robert Smith, Sarah Teather and John Thurso.

Not on the list, but of particular interest to political observers, is party president Tim Farron. A few news outlets say he is still deciding on his vote, even if the Coalition for Equal Marriage thinks he's in the bag. Farron is a frontrunner for the leadership after Clegg, but Lib Dem members might struggle to put their faith in him if he fails to behave liberally on hot topic issues like gay marriage. As a committed Christian he also has a record on abortion votes which some Lib Dems would find troubling. His office was not available for comment yesterday.

Labour is expected to see about 25 MPs vote against the bill, including Austin Mitchell and Stephen Pound, leaving an overwhelming majority voting for it.

A few opposition frontbenchers were expected to vote against the bill, but Labour sources told all the shadow Cabinet would vote in favour. However, shadow minister Rob Flello is expected to vote against the bill, while Gavin Shuker and Stephen Timms will abstain.

Three Labour MPs – Joe Benton, Jim Dobbin and Mary Glindon – wrote an open letter protesting the plan to "redefine marriage" with Lord Anderson of Swansea in December last year.

All three main parties have made the issue a free vote.