Donald Trump is a “would-be dictator” who will fail and Theresa May will not last because of the Brexit “divorce”, billionaire business magnate George Soros has told the Davos world economic forum.

The Hungarian-American investor, on the eve of Mr Trump’s inauguration, delivered a cutting verdict on the incoming President.

The 86-year-old also said he was an “imposter and con-man” who was “gearing up for a trade war” which would have far-reaching consequences on the rest of the world.

Palestinian demonstrators take part in a protest against a promise by Donald Trump to re-locate the US embassy to Jerusalem, in the West Bank city of Nablus on 19 January Reuters (Reuters)

“I personally am convinced that (Trump) is going to fail,” Mr Soros said, in an interview with Bloomberg Television at the Swiss town.

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“Not because of people like me who would like him to fail, but because the ideas that guide him are inherently self-contradictory.”

Mr Soros, who donated $1m (£810,000) in June 2015 to Priorities USA Action which supported Hillary Clinton’s campaign, also said Mr Trump “didn’t expect to win, he was surprised”.

Mr Trump however, and Russia President Vladimir Putin, said he knew he would win.

Former travel salesman Mr Soros also told business leaders and journalists in Davos that he expected financial markets to “not do very well” because of the uncertainty surrounding the Trump administration.

Moving on to the UK’s attempts to leave the European Union, he raised the prospect of the country re-joining the union within just three days of leaving it.

“In my opinion it is unlikely that Prime Minister May is actually going to remain in power. Already she has a very divided cabinet, a very small majority in Parliament. And I think she will not last,” said Mr Soros, who was nicknamed The Man Who Broke the Bank of England because of his $10bn (£8.1bn) short sale of sterling in 1992.

“At the moment the people in the UK are in denial.

"The current economic situation is not as bad as was predicted and they live in hope. But as the currency depreciates, and inflation will be the driving force, this will lead to declining living standards.

Donald Trump supporters attend pre-inauguration concert

“This is going to take some time, but when it does happen they’ll realise that they are earning less than before because wages won’t rise as fast as the cost of living.

“The divorce is going to take a very long time. It’s much harder to divorce than to get married, so I think the desire for rapprochement will develop, and in theory or maybe even in practice you could have a situation in 2019 or 2020 when Britain will leave the EU, because it does have to take place, but they could leave on a Friday but join over the weekend and have the new arrangement in place on Monday morning.”

It followed US Vice President Joe Biden’s stinging attack at the forum on the world's richest one per cent, and Chinese President Xi Jinping warning against isolationist trade wars.