EU referendum pledges and 2015 general election result
17 March 2014 Last updated at 12:26 GMT
Ed Miliband's announcement that a Labour government would not hold a referendum on Europe, without another transfer of powers from Britain to Brussels, has tried to clarify Labour's stance on the EU.
UKIP said this has shown how mainstream parties cannot be be trusted. While Conservatives reckon the Labour policy could see eurosceptics warm to them.
In a Sunday Politics film, Giles Dilnot reports on where parties stand on the referendum and how it may affect the 2015 general election result.