The Conservatives were in disarray over Europe last night after William Hague declared that the party would not accept a vote in Parliament to ratify the EU reform treaty.
Mr Hague, the shadow Foreign Secretary, sparked fury from pro-Europeans and threw the Conservative high command into confusion after appearing to suggest that the party would press for an unprecedented referendum on the treaty even if it is backed by the Commons and the Lords.
He was accused of threatening Britain with "years of instability" by telling MPs that ratification of the treaty "would not be acceptable to a Conservative government and we would not let matters rest there".
An attempt to either hold a referendum or renegotiate the treaty after it had been accepted by Parliament would be seen by other European states as a declaration of war and could even provoke demands for Britain to leave the EU.
David Cameron had previously refused to say whether the party would insist on a referendum after the treaty is ratified.
Mr Hague's comments overshadowed a planned major policy announcement by the Conservatives on council tax and drew an immediate rebuke from the pro-European Conservative MP Kenneth Clarke. The former chancellor challenged Mr Hague to make it clear whether he was pledging to repudiate the treaty or call a referendum. He warned: "I would have thought in the past we have always accepted past treaty obligations by past British governments whenever we have taken office."
Ministers also hit out angrily at Mr Hague, accusing him of caving in to Conservative eurosceptics.
Mr Hague told MPs in the Commons: "If we don't succeed in forcing a referendum in this House and if we fail to win in another place (the Lords) and if all EU member states implement the treaty and if an election is held later in this Parliament, which is a lot of ifs ... then we would be in a situation where we had a new treaty in force that lacked democratic legitimacy in this country and in our view gave the EU too much power over our national policies. This would not be acceptable to a Conservative government and we would not let matters rest there."
When challenged to say whether he was pledging to hold a referendum after the treaty was ratified, Mr Hague replied: "It means what it says it means, exactly what I said earlier ... remember that this is a government that promised a referendum. We all promised, all political parties in this House promised a referendum before the ratification of this treaty."
But Mr Clarke warned: "It seems to me that the alternatives are repudiation of a treaty which this country has ratified, an attempt to renegotiate it or reopen it or a parliamentary process of some kind, or a referendum."
Mr Hague's comments came as a survey of 70 Conservative candidates for the website Conservativehome.com found them overwhelmingly Eurosceptic. Sixty-four of the candidates agreed that too many powers had been transferred from Britain to Europe while only two thought that Britain's relationship with the EU was about right.
David Miliband, the Foreign Secretary, immediately condemned Mr Hague's comments. He said: "This is proof that Euroscepticism in the Tory Party is back with a vengeance. A referendum once the treaty has been signed and sealed by all 27 member states would be bad for Britain, leave us isolated in Europe and would mean years of instability and uncertainty."
Jim Murphy, the minister for Europe, said Mr Hague's comments were an "extraordinary shift" in policy for the Tories. He added: "This latest commitment shows David Cameron has yet again caved in. This rash pledge demonstrates that the Conservatives are not a serious party ready for government."Reuse content