The last few days have seen Tory MPs scrapping with each other over the details of an EU referendum, but now the spotlight is about to turn on Nick Clegg.
With David Cameron still away in New York, the Lib Dem leader has to stand in for him at prime minister's questions. The deputy prime minister will be facing Harriet Harman, but with Labour's Europe policy unclear she is unlikely to want to highlight the issue.
Tory backbenchers however, will have different ideas. The prime minister insisted yesterday that if he were leading a Conservative-only government "we would just get on and legislate" for a referendum. And Grant Shapps is reported to have told off Nick Clegg for showing "complete disdain" for the British people for refusing to back an in/out referendum.
Awkwardly for Clegg, the 2010 Lib Dem manifesto included a commitment to hold such a referendum. Tory backbenchers of the Peter Bone type will want to know what has changed.
Lib Dem 2010 Manifesto:
The European Union has evolved significantly since the last public vote on membership over thirty years ago. Liberal Democrats therefore remain committed to an in/out referendum the next time a British government signs up for fundamental change in the relationship between the UK and the EU.
Clegg will argue that the commitment stands as there has yet to be "fundamental change" in the relationship between the UK and the EU. But Conservative backbenchers are unlikely to let that get in the way of a chance to call him a hypocrite for blocking government legislation.
There also, of course, the small matter of this Lib Dem leaflet printed in 2008 at the time the Lisbon Treaty was making its way through the Commons - which calls for a "real referendum" on Europe.
It's been over thirty years since the British people last had a vote on Britain's membership of the European Union.
That's why the Liberal Democrats want a real referendum on Europe. Only a real referendum on Britain's membership of the EU will let the people decide our country's future.
But Labour don't want the people to have their say. The Conservatives only support a limited referendum on the Lisbon Treaty. Why won't they give the people a say in a real referendum?