THE rift within the Coalition on Europe is laid bare today with Liberal Democrat Vince Cable warning David Cameron not to take a "dangerous gamble" with Britain's national interest just hours before the Prime Minister delivers his landmark speech on the EU.

The Business Secretary, in a speech to business leaders, will say the uncertainty created by talk of a referendum was "potentially driving away investors and the jobs they create".

Mr Cable will recognise the scope for "far-reaching reform" in Brussels and the need to address a "democratic deficit of popular disenchantment" about EU membership but he will stress this is "a terrible time to have the diversion and uncertainty which the build-up to a referendum would entail".

Yesterday, during a heated clash at Prime Minister's Questions, Mr Cameron refused to deny suggestions that he would allow Conservative Cabinet ministers to campaign for British withdrawal from the EU.

It is thought as many as nine Tory Cabinet ministers could be prepared to campaign for a UK withdrawal if significant powers are not repatriated.

Ed Miliband accused the PM of "losing control" of his party over the EU after Mr Cameron failed to give a direct answer to his question about whether he believed Britain would still be a member in five years' time.

The Labour leader warned him that he would not be able to shut down internal party and Coalition differences with a long-awaited speech on Europe in Amsterdam tomorrow, when the Prime Minister is expected to offer a referendum after the 2015 General Election on a renegotiated settlement for UK membership.

"The problem is this: he thinks his problems on Europe will end on Friday," said Mr Miliband, adding: "They are just beginning."

In a political pre-emptive strike, Douglas Alexander, the Shadow Foreign Secretary, will today in a speech call for "reform in Europe not exit from Europe" and say for many Tories getting Mr Cameron to "commit now to an in-out referendum is not about securing consent, it is about securing exit".

Mr Cameron accused Labour of not wanting to give the British people a say on Europe and said the 2015 election would present voters with a simple choice: "If you want to take power back for Britain you vote Conservative, if you want to give power to Brussels you vote Labour."