The Conservatives' divisions over Europe are harming rather than helping the party's standing with the voters, according to The Independent's latest "poll of polls".
The findings call into question claims by Eurosceptic Tory MPs that the party will be more "in touch" with the public if it addresses the EU issue head on.
In a month which saw the eurozone debt crisis and a rebellion by 81 Tory MPs demanding a Europe referendum, the Tories' average poll rating dropped two points to 35 per cent, while Labour's rose one point to 39 per cent. The Liberal Democrats are unchanged on 12 points. Such figures would give Labour an overall majority of 38 at a general election.
John Curtice, Professor of politics at Strathclyde University, who compiled the statistics, said the British public appeared to share the feelings of the Tory Eurosceptics, with growing support for withdrawal or renegotiating Britain's terms of membership.
But he said: "The trouble was that the European debate reminded voters of Tory divisions on the issue. The lesson for the Tories seems to be that they can only hope to profit from Europe if they can be seen to deliver."
This suggests Mr Cameron may have been right to tell his party to "stop banging on about Europe". Despite that, Tory Eurosceptics believe the Prime Minister must respond to the euro crisis by setting out a harder strategy on the EU.
According to Professor Curtice, Mr Cameron reaped no political dividend from the successful military operation in Libya.
Nick Clegg will today issue a warning that the EU will "wither" unless it adopts economic reforms. Addressing the European Parliament in Brussels, the Deputy Prime Minister will argue that, even if the eurozone crisis is resolved, the EU risks being sidelined by the economic powerhouses of China and India because it faces a "crisis of competitiveness".
Mr Clegg, a former MEP and European Commission official, is seen in Brussels as a pro-European but will stress in his speech that he is not a "Euro-fanatic".
He will press home his demand for change in talks with Herman Van Rompuy, President of the European Council, and four European Commissioners. Mr Clegg will say: "Unless this continent becomes more competitive it will find itself in perpetual decline. And even if we are successful now in pulling Europe's economy back from the edge of a precipice, unless we deal with these underlying weaknesses, in five, 10, 15 years we will find ourselves in crisis again... Reform now or regret it forever."
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