London (AFP) - Billionaire investor George Soros has donated £400,000 to a campaign for influencing British lawmakers to vote against a final Brexit deal, its director said Thursday amid accusations of a "plot to thwart Brexit".

"Through his foundations he has contributed £400,000 (453,000 euros, $555,000)," said former minister Mark Malloch-Brown, chairman of Best for Britain, which advocates for the country to remain in the EU.

The Daily Telegraph, a staunchly pro-Brexit newspaper, said Soros's "campaign to overturn Brexit" was planning nationwide adverts this month "which they hope will lead to a second referendum to keep Britain in the EU."

But Malloch-Brown defended the campaign, saying it was "perfectly reasonable" that Members of Parliament should have a chance to think again about going ahead with Brexit.

"There are a lot of people out there who are frustrated," he told BBC radio, adding: "A majority of MPs are still personally Remainers and yet are about to vote for anything between a hard and a soft Brexit."

Soros, 87, a US financier and philanthropist, is a favourite bete noire of nationalists around the globe from the Kremlin to his native Hungary.

He is a hate figure in Britain for making a billion dollars betting against sterling on Black Wednesday in 1992 when Britain was forced to withdraw the pound from the European Exchange Rate Mechanism.

In a speech at the World Economic Forum in Davos last month, Soros predicted that British Prime Minister Theresa May's spell in power would not last long and said British people were "in denial" about the financial consequences of leaving the EU.

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

"It's going to take some time but when it does happen, they will realise that they are earning less than before, because wages won't rise as fast as the cost of living," he said.