Opposition Labour leader Ed Miliband Wednesday effectively ruled out a referendum on Britain's membership of the EU before 2020 if he wins next year's election, except in the "unlikely" event of a further transfer of powers to Brussels.
Prime Minister David Cameron has promised an in-out referendum in 2017 provided he is re-elected, a pledge which has raised major questions about Britain's future in the European Union.
In an article in the Financial Times setting out his strategy clearly for the first time, Miliband said the Conservative leader's timetable was "arbitrary" and would be a distraction from the economic issues facing Britain.
While Labour believes Britain's future is in the EU, Miliband said he recognised concern about moves towards an ever-closer union, which "is not Labour's vision".
A law already exists requiring a referendum on any further transfer of powers away from the British parliament, but Miliband said he would bring in legislation to ensure that vote would be on whether to stay in or leave the EU.
He stressed however: "It is unlikely there will be any such proposals in the next parliament", which will run from 2015 to 2020.
Such a position effectively rules out Labour calling a referendum before 2020 if it is in power.
"This position, setting out the conditions in the next parliament under which a Labour government would hold an in-out referendum, offers the British people a clear choice at the next election," Miliband wrote.
Miliband's comments are likely to be welcomed by pro-European members of his party, but Labour also has a significant number of eurosceptics who wanted him to match Cameron's promise.
A YouGov poll in October found 62 percent of Britons wanted a referendum, against 21 percent who did not. Among Labour voters, the figures were 49 percent and 33 percent.
Labour backbench MP Graham Stringer said it was a "shoddy compromise", adding: "This is so ambiguous as to be impossible to sell on the doorstep."
But former foreign secretary Jack Straw, seen as a eurosceptic among Labour MPs, welcomed the announcement.
"This offers reassurance not only to business and millions of workers whose jobs depend on Europe but also allays the fears of those who are uncomfortable with moves towards ever-closer union," Straw said.
In an attempt to mollify restless Tory eurosceptics, Cameron announced in January 2013 that he would renegotiate Britain's membership of the EU to better reflect voters' concerns and then put it to a vote.
But he is struggling to find support among fellow EU leaders for the changes he wants.
Cameron said: "By his own admission, Ed Miliband says it's unlikely there'll be an in-out referendum on Europe under Labour.
"Only the Conservative Party can guarantee and deliver that referendum."
Despite the strong feelings on both sides, opinion polls suggest Europe is not a high priority for voters, who cite the economy and immigration as their top concerns.
Immigration is linked to the European issue, however, because Britain's EU membership makes it powerless to stop large numbers of EU workers arriving -- 209,000 in the year to September 2013, up from 149,000 the previous year.
Cameron has called for reforms of freedom of movement in the EU and his government has imposed restrictions on the level of state benefits EU citizens can claim.
In his article, Miliband also urged action to relieve "anxieties" about immigration, including reforms to make it harder for citizens of new EU states to work in Britain.