In a desperate attempt to dissuade Tory MPs from voting in favour of a referendum on EU membership next Monday, William Hague takes to the pages of the Telegraph today. The great eurosceptic writes:

As a Conservative, I want to bring powers back from Europe, as we set out in our election manifesto. But a referendum on Britain's membership of the EU, especially at this time of profound economic uncertainty, is not the answer.

It's noteworthy that all three of the main parties are now ordering their MPs to vote against the Commons motion (currently supported by 86 MPs). But here's an inconvenient truth: one of them previously supported an in/out referendum. In their 2010 election manifesto, the Lib Dems called for a national vote on Britain's EU membership. Here's the pledge in full:

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.

And here's the text of the Commons motion:

That this House calls upon the Government to introduce a Bill in the next session of Parliament to provide for the holding of a national referendum on whether the United Kingdom should

(a) remain a member of the European Union on the current terms;

(b) leave the European Union; or

(c) re-negotiate the terms of its membership in order to create a new relationship based on trade and co-operation.

True, the Lib Dem pledge contains a notable caveat ("the next time a British government signs up for fundamental change") but as the Guardian's Nicholas Watt notes, that didn't stop Clegg walking out of the Commons on 26 February 2008 when the then speaker, Michael Martin, refused to call a Lib Dem amendment demanding a referendum. After Ed Davey (then the party's foreign affairs spokesman) was expelled from the chamber, Clegg said:

I share the dismay of [Ed Davey]. What guidance can [the deputy speaker] give me on how we can secure - if not today, at some point during the remaining stages of the Bill - the opportunity to debate the issue that many members want debated and many members of the public want debated: our future membership of the EU?

Davey's words were even more striking:

Will the chair reconsider the decision not to select the Liberal Democrat amendment for a referendum on Britain's membership of the EU? That is the question that goes to the heart of the debate before the House. That is the debate that people want to hear. We are being gagged, Sir.

Like Keynes, the Lib Dems can argue that when the facts change, they change their mind. The holding of a referendum on Britain's EU membership is not a credible response to the current crisis. But Clegg's latest U-turn will only increase his reputation for inconsistency.