George Soros was told to 'butt out' last night after it emerged the billionaire is bankrolling efforts to keep Britain in the EU.

Senior Tories raised the alarm after the American financier confirmed he had donated more than £700,000 to groups working to water down or block Brexit.

Mr Soros famously bet against sterling on Black Wednesday in 1992 – earning him £1billion and the nickname 'the man who broke the Bank of England'. The fiasco cost taxpayers £3.3billion.

Best for Britain, which has received £400,000 from Mr Soros, admits its campaign for a new referendum could cause the Government to fall.

The group should hand back the cash, according to Iain Duncan Smith.

The former Conservative leader said it was wrong for foreign plutocrats to 'undermine democracy' in Britain.

Billionaire investor George Soros, pictured in Brussels last year, is said to have handed £400,000 to a campaign arguing against Brexit

Lord Lamont, a former Tory chancellor, said: 'George Soros is a brilliant financier, but he should stick to finance and stay out of British politics.'

Conservative MP Henry Smith said Mr Soros should 'butt out'.

As Downing Street insisted Britain will leave the EU in March next year even if MPs vote down a divorce deal:

- Best for Britain co-founder Gina Miller, who has since quit the group, said it had become 'undemocratic';

- Its leader said ditching the referendum result would be like abandoning a wet holiday in Cornwall;

- Mr Soros was said to be so angry at the criticism that he was considering a further six-figure donation;

- It emerged that his money could be funding six UK organisations, including a parliamentary group dedicated to watering down Brexit;

- David Davis condemned EU threats to punish Britain if it stepped out of line during a transition period;

- Cabinet ministers agreed to pursue an 'ambitious' trade deal with Brussels that would allow the UK to diverge from its rules.

Gina Miller, the millionaire businesswoman who took the Government to court over Brexit, promised 'the biggest tactical voting effort in our history' when she launched the Best for Britain campaign in April last year

Best for Britain made a presentation to six Tory donors at Mr Soros's Chelsea home this week, the Daily Telegraph reported. They were told the group aims to pressure MPs into voting down a Brexit agreement negotiated by Theresa May in the autumn.

A document circulated to those present said if they were successful 'it is likely to trigger a new referendum, or election'. It added: 'We must prevail decisively, so reassuring Europe that our return will be permanent.'

The group, which is expected to launch a mass advertising campaign next month, said it would use 'guerilla marketing tactics'. It said its aim was to 'wake the country up and assert that Brexit is not a done deal. That it's not too late to stop Brexit'.

None of the Tory donors at the presentation is thought to have pledged any money. Mr Soros's donations were revealed yesterday.

Tory MPs last night said Mr Soros, who was born in Hungary, had no right to try to undermine the result of the largest democratic exercise ever undertaken in Britain.

Mr Duncan Smith said: 'However this is dressed up, George Soros is interfering in the British political system

'I do have a problem with people taking money from wealthy non-British citizens to undermine the democratic process in this country.

'They should give it back – if they can't raise the money in this country then they should not be doing it.'

Henry Smith said: 'George Soros has never been a friend of Britain's best interests. As a US citizen he should butt out of telling the UK they should remain under Brussels' yoke.

'Serious questions need to be asked as to how a foreign national can be funding a British political campaign.'

Jacob Rees-Mogg, a leading Conservative Eurosceptic MP, said the revelations underlined the need for Brexit supporters to keep making the case to leave the EU.

'It is quite clear there is a lot of money behind the continuing Remain campaign and a lot of Establishment support for overturning Brexit,' he added.

'We must keep making the arguments that Britain will be better off out of the EU.'

Mr Soros (pictured with EU commission President Jean-Claude Juncker in 2017), previously said it was possible that the UK would apply to rejoin the European Union soon after Brexit

One pro-Brexit minister said Remain forces were trying to 'demoralise' the British public and 'delay' Brexit in the hope of overturning it.

Tory MP Peter Bone added: 'This is more evidence of an Establishment push to overturn the referendum result.

'It is being run by people who take the view they know better than the British people and that the people who voted for it are stupider than they are. That is the complete reverse of the truth.

'No one should underestimate the effort they are putting in. This is a significant push being orchestrated in secret and bankrolled by very wealthy individuals. No one should think that winning the referendum guarantees Brexit will be delivered.'

The Prime Minister's official spokesman said Mr Soros was entitled to fund political campaigns. But he insisted that Mrs May would not be deflected from her pledge to respect the referendum and lead Britain out of the EU next year.

WHO ARE BEST FOR BRITAIN AND WHAT DO THEY WANT? Best for Britain was launched by Gina Miller as a campaign to encourage tactical voting against Brexit Best for Britain is a campaign group dedicating to moderating and ultimately reversing Brexit. It was launched by Gina Miller, the former model who successfully challenged the Government in court over to Article 50, to encourage anti-Brexit tactical voting at the election. Ms Miller left the group soon after the election and former Labour minister Mark Malloch-Brown took over as chairman. The group is actively fundraising for its efforts to frustrate Brexit. As well as big money donations from people like George Soros, it run crowdfunding - including a new campaign to 'stand up for free speech'. It urged MPs to vote against the flagship Brexit Withdrawal Bill and campaigns to protect universities from what it describes as a right-wing witch hunt. The group draws cross party support, frequently issuing statements from MPs including Daniel Zeichner from Labour, Tom Brake from the Lib Dems and Green Caroline Lucas.. The board includes former Olympian Stephen Peel economist Anatole Kaletsky, businessman Clive Cowdery, while the CEO is activist Eloise Todd. Advertisement

He confirmed that the Commons vote this year would be a question of 'deal or no deal', adding: 'The PM's position is clear. The country voted to leave, that is what we are going to deliver and there will not be a second referendum.'

Sources at Best for Britain yesterday denied claims that the group has operated in a 'shadowy' manner, saying it had always been clear about its aim of stopping Brexit.

As well as running its own campaign, the group is planning to fund other anti-Brexit organisations, including Open Britain.

It also funds the all-party parliamentary group on EU relations, which is working to water down Brexit in parliament.

Prominent members include former Tory minister Anna Soubry and former Labour cabinet minister Lord Adonis, who has pledged to 'sabotage Brexit'.

Mr Soros has spent millions promoting democracy movements around the world through his Open Society Foundation.

In a statement last night the foundation said its grants to anti-Brexit campaigns were in line with its 'worldwide mission to build vibrant and tolerant democracies whose governments are accountable to their citizens'.

The group's president Patrick Gaspard added: 'A fundamental principle of open societies is that people get to decide how they are governed, knowing exactly what they stand to gain and what they stand to lose.'

Miss Miller said the public had a right to know who was backing Best for Britain.

Lord Malloch-Brown, who chairs the group, told the BBC that MPs should ignore the referendum result and vote down whatever deal Mrs May secures with Brussels.

He suggested that reversing the referendum result because of fears the economy would suffer was comparable to simply changing holiday destinations because of the weather.

He said: 'It's like being told let's go to Cornwall for a beach holiday and it's going to be sunny and it rains every day and you're allowed to change your mind.

'There are a lot of people out there terribly frustrated, growing in numbers. So we're putting together a campaign which is actually democratic in its funding too, It's got some big donors including I'm very proud to say George Soros but also thousands of small donors as well.'

He said his goal was to 'mobilise public opinion in favour of Remain in order to bring that change in public opinion to bear on parliament when it has the meaningful vote on Mrs May's Brexit package sometime at the end of this year'.

He claimed the referendum had betrayed British democracy and urged MPs to ignore the result, adding: 'I wish MPs would take responsibility for this and would be willing to vote on their conscience and their knowledge of the issues and then face their electors at the next election.'

He laughed off claims he was trying to subvert democracy and insisted he was trying to 'empower' it instead.