Billionaire investor George Soros has defended his decision to hand £400,000 to a campaign arguing against Brexit - and says he considers leaving the EU a "tragic mistake".
Mr Soros came under fire last week after it was revealed he had donated the money, through one of his foundations, to Best for Britain.
The tycoon has now hit back at what he described as "toxic personal criticism" against him, and has denied accusations that he was "undermining democracy".
Writing in the Mail on Sunday, he told how the organisation had his "wholehearted support", and insisted he had never made a secret of his opposition to Brexit.
He said: "The fact that conditions are unsatisfactory does not mean that they can't get worse. That is what has happened in Britain.
"Before the referendum Britain was doing better economically than the rest of Europe. But this has now been reversed, with Continental economies powering ahead while Britain lags behind."
Hungarian-born Mr Soros, one of the world's richest men who made a billion dollars betting against sterling on Black Wednesday in 1992, said Britain would "lose much of its global influence" outside of Europe.
He added: "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 also claimed Brexit had turned young against old, saying young people had become disillusioned with democracy after older votes "overruled" them in the referendum.
Declaring to be a "proud supporter" of Best for Britain, he warned that the effect of the uncertainty created by Brexit would become "painfully obvious" in the next six months as negotiations entered the "most contentious phase".
Mr Soros's donation to Best for Britain was first reported in the Daily Telegraph, in a story written by a team including Theresa May's former chief of staff Nick Timothy.
Mr Timothy, who backed the Leave cause, used his column in the newspaper to claim that Best for Britain wanted to bring down Mrs May's government.
He wrote: "The objective is to convince MPs to vote against the deal Theresa May negotiates with Brussels, regardless of its content and despite the risk that doing so could mean Britain leaves the EU with no alternative agreement in place.
"Malloch-Brown and his backers believe that, if Parliament rejects the Brexit deal, the Government will fall, and Brexit can then be stopped."
But Lord Malloch-Brown, chairman of Best for Britain, said: "We think the British people deserve a final say on the Brexit deal and believe the country has been led down a dangerous false turn.
"This is a democratic and patriotic effort to recover our future and we welcome support for our efforts from many quarters."