Nick Clegg has been accused of hypocrisy for opposing an EU referendum, as he was assailed by Tory backbenchers for blocking a bill that would legislate for a ballot by 2017.
Standing in for David Cameron at prime minister's questions on Wednesday, the Lib Dem leader said Conservatives were trying to "change the goal posts" as the coalition had already passed a law that would trigger a referendum should there be any further transfer of power from Westminster to Brussels.
"We should have a referendum on Europe when the rules change," he said. "We said that at the time of the Lisbon Treaty. And we said it in our manifesto. We have legislated on it and we shall say it again."
Traditionally prime minister's questions is a battle between the government and the opposition, however today's session was dominated by exchanges between Clegg and the eurosceptic Tory MPs behind him.
No less than five Conservative backbenchers stood, some brandishing Lib Dem campaign leaflets, to accuse the deputy prime minister of going back on his word to hold a "real referendum" on the EU. In 2008 Clegg appeared on a leaflet that declared: "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."
Edward Leigh asked: "Was the man an imposter or just a hypocrite?" And James Gray said as a "great democrat" Clegg should stand by the "precise wording of this very fetching Lib Dem leaflet" that somehow found its way onto his desk.
Clegg he had "done better" than that as laws passed by the coalition meant there would be a referendum should more powers pass to the EU. And given the big changes underway in the bloc, he predicted it was inevitably a matter of "when not if" a poll would have to take place.
Yesterday David Cameron attempted to quell Tory unrest by publishing a draft EU referendum Bill that will be handed to a backbencher to introduce as a Private Members Bill. However without government time such a Bill would be unlikely to pass. And Clegg sidestepped the question when asked if he would allow government time in the Commons - suggesting it would be denied.
Later this evening at least 70 Tory MPs are expected to take the almost unprecedented step of voting in favour of an amendment to the Queen's Speech that would condemn the government for failing to legislate for an EU referendum by 2017.
Clegg MPs should "stick to the priorities of the British people which is growth and jobs" rather than obsessing over Europe. And he asked Tories which piece of legislation they would like to dump from the Queen's Speech to make room for an EU referendum bill. "We on this side of the House should go out and promote what's in it not spend days bemoaning what's not in it," he added.
In the absence of Cameron, Ed Miliband's place at prime minister's questions was taken by Harriet Harman. Labour's deputy leader wanted to know how Cameron would vote on the amendment were he not in New York.
"If the prime minister was here today, would he be voting for the government, against the government or showing true leadership and abstaining?" she asked. "While the prime minister is bogged down in confusion about Europe people are suffering."