The European Union "may not survive" the "long-lasting" economic stagnation caused by the eurozone crisis, billionaire hedge-fund manager George Soros has warned.
"Japan just had 25 years of [stagnation] and now it's desperately trying to get out from exactly the situation that the euro is moving into."
The business magnate told BBC Radio 4's Today programme that eurozone countries were set to face "political crises" due to the euro and the mounting debate over Britain's membership of the European Union.
Soros threw his weight behind Britain staying as a member of the European Union, saying: "Any sensible politician would try to preserve the current position if at all possible because Britain actually has the best of all possible worlds right now being the member of the common market and not being a member of the euro.
The investor's intervention comes after David Cameron promised a referendum on Britain's membership of the European Union by 2017. By contrast, Labour leader Ed Miliband has effectively ruled out a poll and only promised to hold a referendum if Brussels demands fresh powers.
The Labour leader stressed his determination to reform the EU if elected in 2015, and pledged a legal lock that would guarantee an in-out vote if Westminster was asked to hand over more control.
But he made clear, in an article for the Financial Times, that he believed that was "unlikely" in the next parliament.
Within minutes of the piece being published, the Prime Minister responded that the only way of securing an in-out referendum was to back the Conservatives.