George Soros hits back at 'toxic, personal criticism' and defends donation to anti-Brexit campaign

• The tycoon had been heavily criticized after it was revealed that, through one of his foundations, he had donated a sizable amount of funds to the Best for Britain campaign.
• Writing in the Mail on Sunday newspaper, Soros said: "I consider Brexit a tragic mistake. … Brexit is a lose-lose proposition both for Britain and for Europe."

Billionaire investor George Soros is defending his right to donate hundreds of thousands of pounds to a pro-European Union campaign aimed at stopping the U.K. leaving the political and economic bloc.

The tycoon had been heavily criticized after it was revealed that, through one of his foundations, he had donated a sizable amount of funds to the Best for Britain campaign, which advocates stopping Brexit and keeping the U.K. in the EU.

In response, Soros hit back at what he described as "toxic, personal criticism" and dismissed accusations that his actions were "undermining democracy."

Writing in the Mail on Sunday newspaper, he said: "I consider Brexit a tragic mistake. … Brexit is a lose-lose proposition both for Britain and for Europe. Politically, Europe without Britain will be weakened in its ability to defend and promote democratic values."

UK and EU should be 'uniting to resist Putin's Russia'

"To make matters worse, the divorce process will preoccupy both Britain and Europe for years ahead, when they should be uniting to resist external enemies like Putin's Russia and resolve the internal contradictions that made some people regard the EU as their enemy," he added.

The Daily Telegraph first reported Soros' donation of £400,000 ($550,000) to the Best for Britain campaign in an article written by a team including U.K. Prime Minister Theresa May's former chief of staff, Nick Timothy.

The newspaper said Soros and two other major donors were backing plans to launch a nationwide advertising campaign later this month with the hope it could lead to a second referendum and potentially keep Britain in the EU.

Hungarian-born Soros is known as the "man who broke the Bank of England" for betting against the pound in 1992 on what became known as "Black Wednesday." The British government was then forced to withdraw the currency from the European Exchange Rate Mechanism.

Last year, Soros suggested the U.K. may never leave the EU if the bloc reforms itself while Brexit negotiations were taking place.

— CNBC's Holly Ellyat contributed to this report.