The Speaker of the Commons, John Bercow, is being urged by MPs not to allow the Government to block demands for a ban on the use of wild animals in circuses.
Ministers plan to head off calls for the practice to be outlawed in a Commons debate on Thursday by tabling a counter-motion which stops short of a ban. There is now a risk that MPs will be able to vote only with the Government motion rather than the backbench call for a ban.
Yesterday senior MPs appealed to Mr Bercow to prevent ministers using this technical device to avoid a vote on stopping the practice.
Mark Pritchard, secretary of the Tory 1922 Committee, who has secured the debate, said: "The Speaker has proved his willingness to be champion of the backbencher many times. I hope that this will be another opportunity. It is important that Parliament is a counter-balance to the government of the day and that the voice of the public is heard through the backbenchers who represent them."
Some 28,400 have signed The Independent's online petition calling for a ban.
Backers of a ban in all parties had been confident that MPs would vote overwhelmingly in favour, but that has now been thrown into doubt by the Government's move to table its own proposal. However, many ministers will have a dilemma on Thursday over whether to vote for the Government, or with their conscience. At least 16 Coalition ministers – 13 Liberal Democrats and three Conservatives – supported a ban on wild animals in circuses while in opposition.
Norman Baker, the Liberal Democrat Transport Minister, campaigned on the issue several times, tabling a Commons Early Day Motion (EDM) in 2005, while the Tory Cabinet Office minister Oliver Letwin seconded an EDM in 2009.
Support for a ban is particularly strong among Liberal Democrats, with all four of the party's cabinet ministers, Deputy Prime Minister Nick Clegg, Business Secretary Vince Cable, Chief Secretary to the Treasury Danny Alexander and Energy Secretary Chris Huhne, backing a ban before last year's general election. It is known that Mr Clegg remains sympathetic to a ban but may miss the vote as he due to be on a visit abroad.
Alistair Carmichael, Lynne Featherstone, Nick Harvey, David Heath, Norman Lamb, Andrew Stunnell, Sarah Teather and Steve Webb signed Commons motions in 2008 or 2009 or both years. Two former leaders now on the Liberal Democrat backbenches, Charles Kennedy and Sir Menzies Campbell, also signed a Commons motion in 2009.
As well as Mr Letwin, other Tory ministers who signed EDMs in favour of a ban are the Education minister Tim Loughton and Transport minister Mike Penning.
Animal welfare groups hope that ministers will miss the vote rather than back the Government's motion.
The Liberal Democrats said their ministers would back the Government. A spokesman said: "The point about coalition politics is that we have to support some things that weren't previously our policies and the Conservatives likewise. That's not a betrayal of principle, that's coalition politics."