Mr Soros said the financial system had to be built up from the foundations
Billionaire investor Gorge Soros has said the G20 summit will be a "make or break" event for the world's economy.
In a BBC interview, Mr Soros said the international financial system had collapsed because it was flawed and it had to be restructured.
Mr Soros say it may be the last chance to prevent a full-scale depression.
He said the G20 meeting had to come up with concrete solutions to help the developing world in particular, which had been been worst hit.
Mr Soros warned that any attempt to pull economies out of recession had to be done co-operatively.
Soros: G20 is 'make or break'
He said: "The G20 meeting is make or break because unless they do something for developing world there will be serious collapse in that part of the world.
"I'm using phrase depression because unless we take the right measures we're liable to end up there.
If countries start doing it [engineering a new financial world order] bilaterally instead of multilaterally, the system will fall apart and we'll end up in depression."
He also said the rebuilding meant the previous economic system had to be scrapped.
The International financial system has collapsed and cannot be restored in its current form
"I don't think we'll ever be back to where we came from. It should be recognised that the last 25 years were an aberration and we cannot go back there. We have to reconstruct the financial system from its foundations up."
Mr Soros said regulators and the financial sector shared the blame for the meltdown, as they "participated in this crazy boom built on false premises on the belief that markets are self-regulating and should be left alone".
Mr Soros also warned the UK economy was in a deep recession "which is going to be a lasting one".
He added: "The International financial system has collapsed and cannot be restored in its current form. It will have to be restructured because it was flawed and collapsed under its own weight."
In May last year, Mr Soros was interviewed by the BBC's business editor Robert Peston and said he was worried about the US and UK's ability to deal with the downturn because of their reliance on credit.
Mr Soros urged wealthy nations to give their allocations of the IMF's internal currency, called Special Drawing Rights, to poorer ones because developing countries were not in a position to bail out their own failing banks.
George Soros famously made his name - and $1bn - when he bet that sterling would have to withdraw from the European Exchange Rate Mechanism in 1992. He's also said to have accurately predicted and profited from the Asian financial crisis in 1997.
The 78-year-old Hungarian is one of the largest aid donors in Africa, having donated around $6bn to his favourite causes.
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