Labour stands on 34%, up 1 point on a fortnight ago, while the Tories are unchanged on 32%. Ukip, which is edging downwards, has dropped 3 points to 15%, while the Greens are up 2 points on 8%, ahead of the Lib Dems, who are also up 2 points, on 7%.
The results will provide some comfort to Ed Miliband and Labour after the party leader came under fire from some leading entrepreneurs for policies they regard as hostile to business and potentially damaging to the UK economy.
The poll suggests that while Labour’s lead remains wafer-thin, the opening shots of the election campaign are not causing further erosion of Labour support or any surge for the Conservatives.
While the Tories lag behind, David Cameron retains a clear lead over Miliband in the personal ratings.
When voters were asked whether they approved of the performance of Cameron, 39% said they approved, against 44% who disapproved, giving the prime minister a net rating of -5 points.
Just 23% approved of Miliband’s leadership against 49% who disapproved, giving the Labour leader a net score of -26.
Opinium also asked a series of questions on the preparedness of supporters of the different parties to vote tactically on 7 May to keep their main opponents out of Westminster, and found Conservatives most willing to do so.
When Tory voters were asked to imagine that only Labour or Ukip could realistically win in their constituency, 30% said they would be prepared to vote Ukip to keep Labour out.
When Labour voters were told to imagine they lived in a constituency where only the Conservatives or Lib Dems could win, 22% said they would vote Lib Dem.
Perhaps surprisingly for a party whose membership is regarded as closer to Labour than the Tories, more Lib Dems said they would vote Tory to keep Labour out (23%) than would opt for Labour in order to prevent a Tory MP winning (13%).
Opinium Research carried out an online survey of 1,947 adults in Great Britain aged 18-plus from 3 to 6 February 2015. Results have been weighted to nationally representative criteria. Full tables and results are available here.
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