Billionaire investor George Soros has warned Scotland could not keep the pound if it became independent.

The Hungarian-born investor said it would not be "actually practical" for Scotland to keep its currency if First Minister Alex Salmond's campaign for independence was to succeed.

Mr Soros was once described as the "man who broke" Britain after making about $1 billion profit by selling sterling on Black Wednesday in 1992, when the UK crashed out of the Exchange Rate Mechanism.

He told the European Council On Foreign Relations in London yesterday: "Scotland wants to remain a part of the (pound) sterling and Britain is creating obstructions to that.

"It would be a very difficult relationship and I do not think Scotland becoming independent and yet remaining part of the sterling is actually possible."

The UK Government has previously ruled out a currency union with Scotland if people vote for independence from the UK in September's referendum.

Chancellor George Osborne, Treasury Chief Secretary Danny Alexander and shadow chancellor Ed Balls united in saying they would not support Scotland keeping the pound if there is a Yes vote.

Speaking at the launch of his new book, The Tragedy Of The European Union: Disintegration Or Revival, the now-retired Mr Soros, 83, said: "The alternative would be for Scotland to seek membership of the European Central Bank and then it would be part of the eurozone.

"I think an independent currency would be very inefficient and potentially dangerous."

Meanwhile, leading economists have queued up to say Mr Salmond must begin putting in place plans for a Scottish currency in the event of a Yes vote.

Out of five experts who appeared before a Scottish Parliament committee, only one believed a currency union was plausible and likely; three virtually ruled it out; and all five rubbished the idea that an independent Scotland should use sterling informally - so-called "sterlingisation".

The creation of an independent currency was therefore seen as the best option, either in its own right, or as a Plan B if negotiations with the rest of the UK to share sterling fell through.

Professor Ronald MacDonald, of Glasgow University, backed a separate currency as the best option.

He told the Economy, Energy And Tourism Committee that being part of a formal monetary union would not enable an independent Scotland to deal with "oil shocks" that come from the "resource curse" that could have "significant knock-on effects for competitiveness of non-oil sector".

He said: "Post-independence, the only option I can see for Scotland is a separate currency. Nothing else will work, nothing else will be credible to the markets."

Dr Monique Ebell, research fellow at the National Institute Of Economic And Social Research, said it would be "difficult to see how a monetary union would be in interests of the rest of UK," adding: "I would agree the most appropriate currency choice would be for Scotland to have its own currency, mainly because this would give Scotland the greatest capacity to react to shocks."

Sir John Gieve, visiting professor at University College, London, and a former Deputy Governor of the Bank of England, saw little likelihood of support from the the rest of the UK.

Professor Anton Muscatelli, the Principal of Glasgow University, and Professor Jeremy Peat, director at the David Hume Institute, made the case for a formal monetary union, with both economists stating a separate currency would be their second choice.

Professor Muscatelli said an oil fund could be used to help "smooth out public expenditure", solving the "hydro carbon problem" highlighted by Professor MacDonald.