George Soros has pledged a further £100,000 to Best of Britain, an anti-Brexit campaign fighting to keep the UK in the European Union, in answer to criticism of his previous donation to the group (£400,000).
Mr Soros raised the money through one of his foundations (Open Society Foundation), as he did on the prior occasion, telling the Guardian that he was "happy to take the fight" to critics.
He told the newspaper that he was sure there was a "smear campaign" against him in the right-wing press after his first donation, adding that they were using it to "prop up their failing case".
In an article for the Mail on Sunday, he said that he had experienced "toxic personal criticism in the recent days".
"I believe passionately in [open society], and this is why I eventually decided to establish the Open Society Foundations and devote my wealth to spreading the benefits of open democracy and helping those that suffer repression.
"Open society is characterised by calm, rational discussion, free from the toxic, personal criticism we have seen in recent days. I am a proud supporter of Best For Britain, a group that wants Britain to remain a member of the European Union. I consider Brexit a tragic mistake."
Despite those attacks, more than 2,300 people had donated to a crowdfunding page set up by Best of Britain after Mr Soros was criticised in the press.
Best of Britain Chief Executive, Eloise Todd told The Guardian, "We live in a democracy, and the right to freedom of speech is precious. Elements of the right-wing press don't seem to agree.
"The UK's future with the EU is not a done deal, there is still a vote to come and people across the country deserve to know the truth about the options on the table: one of which is staying and leading in the EU."
The famous investor had already said in previous interviews that the Britain's exit from the EU was a "tragic mistake" and that Britain may wish to rejoin shortly after Brexit.
Recently, he said, "Since Brexit is a lose-lose proposition, it follows that a parliamentary vote to stop Brexit would be its opposite.
"But a mere reversal of the 52:48 majority for Brexit is not enough.
"The majority for staying would have to be significantly larger to convince Europe that Britain's attitude towards Europe has fundamentally changed and its decision deserves to be taken seriously."