Ken Clarke has pleaded with Tory MPs to "move on" from the debate over the European Union, as backbenchers insisted they would press ahead with plans to vote against the government's Queen's Speech.
The europhile Conservative cabinet minister said the focus should instead be the result of the referendum and that leaving the EU would be a "catastrophe".
"David Cameron has already committed the Conservative Party to holding a referendum on Europe in the next Parliament; this is obviously an attempt to underline that commitment to a referendum if he gets the chance," Clarke said.
"I think we should move on now. The important thing is to make sure we get the right result from any referendum which is held to avoid the catastrophe for the country's economy and our political standing in the world if we were to be so very, very reckless as to leave the European Union."
On Tuesday the Conservative Party will publish draft legislation paving the way for a referendum by 2017 on the UK's membership of the EU and then offer it up to a backbench MP to table it as a Private Member's Bill.
Cameron is unable to put the Bill forward as government legislation because of opposition from his Liberal Democrat coalition partners who are opposed to a in/out referendum.
But foreign Secretary William Hague said the move would force Labour and the Lib Dems to "show their hand" on Europe and make clear whether they are willing to match the Tories' commitment to offer the public a referendum following renegotiation of Britain's relationship with the EU after the 2015 election.
Amid Labour claims that Cameron has lost control of his party, Hague insisted that the PM had been looking for some time for ways to strengthen his commitment to a referendum.
And Hague insisted the timing of the publication was dictated by the ballot in the House of Commons on Thursday to choose which MPs will be allowed to table Private Member's Bills, and not by the strong showing for the eurosceptic UK Indepence Party in this month's council elections.
However Tory backbencher Philip Hollobone said the prime minister's decision to announce the draft referendum bill while on a foreign trip in the United States was "undignified". He told BBC Radio 4's World at One programme: "There is some chaos in No.10 this week."
The Conservative Party's internal debate about the EU has echos of the battles of the 1990s which sharply divided John Major's government. Sheila Gunn, who served as Major's press secretary, told The Huffington Post UK the obsession with Europe was "depressing" in its familiarity.
"You could also say now that the Conservative Party is handing the election to the Labour Party," she said.
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