Labour will abstain in a crunch House of Commons vote on the referendum on Britain's membership of the European Union next month, the party said today.
Conservative backbencher James Wharton has tabled a private member's bill requiring an in/out referendum to be held by the end of 2017, with the support of party leader David Cameron, who was unable to bring the legislation forward as a government bill because of opposition from Liberal Democrat coalition partners.
Labour dismissed the bill as "a Tory gimmick and a political stunt" and said its MPs would not turn up to vote when it has its second reading in the Commons on July 5.
Mr Cameron has imposed a three-line whip on Tory MPs to turn up and take part in the vote, which is happening on a Friday, when many MPs normally leave Westminster to work in their constituencies.
Labour leader Ed Miliband made clear that he does not expect his MPs to attend Parliament to vote on the EU bill, though aides said it would not be regarded as a disciplinary issue if some chose to do so.
The decision means that the bill will almost certainly receive a second reading, but nevertheless Labour believes it will not succeed in reaching the statute book by the cut off date of May 2014, when the parliamentary session comes to an end.
A senior Labour source said: "Our view of this bill is that it is a Tory gimmick and a political stunt and therefore we do not need people to be here on July 5. It is an irrelevant bill.
"We will not be voting on this bill at second reading. We are absolutely certain that this bill is not going to make it to the statute book. It is a bill of major constitutional change and there is very wide scope for amendments that would allow the bill to be delayed significantly - almost certainly beyond the May 2014 deadline."
Even if it does get through the Commons, the bill is unlikely to survive passage through the House of Lords, where Conservatives are not the largest party, said the source.
"It is our view that it is quite wrong to legislate for an in/out referendum in 2017 which would create four years of uncertainty, putting at risk the national interest and damaging British jobs and the economy," added the source.