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Left-wing billionaire George Soros is pumping hundreds of thousands of dollars into a campaign looking to sabotage British voters’ 2016 decision to leave the European Union.

The U.K. Daily Telegraph first reported late Wednesday that Soros has delivered £400,000 ($560,000) to the anti-Brexit "Best for Britain" campaign via his Open Society Foundations.

He also hosted big-money donors at his London home as part of the group’s goal to raise support to nix the implementation of the Brexit referendum.

Best for Britain is currently led by Lord Mark Malloch-Brown -- a fomer diplomat and U.N. deputy secretary-general -- and is reportedly planning a massive ad campaign to push for a second referendum to make voters rethink the decision to leave the E.U.

“George Soros’ foundations have, along with a number of other major donors, also made significant contributions to our work,” Malloch-Brown told Reuters. He also confirmed that the £400,000 number was accurate.

Open Society Foundations said that the funding for Best for Britain was one of a number of Brexit-related grants the organization had made, including a £182,000 grant to European Movement U.K.

“Human rights protections, hard-won civil and labor rights, safeguards on key issues such as clean air or food standards are at stake here for British citizens,” Patrick Gaspard, president of the Open Society Foundations, said in a statement. “It is essential that they are informed and empowered to make decisions about the future relationship between the U.K. and the E.U."

“The Open Society Foundations support British groups striving to ensure that this crucial debate is not shut down. 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,” Gaspard, a former Obama White House political affairs director, said.

Soros has used his financial muscle for years to push left-wing causes across the globe. In Davos, Switzerland, last month, Soros said his Open Society Foundations is funding more institutions in the U.S. to ensure a Democratic victory in November.

The Telegraph reports that Best for Britain is planning mass rallies, concerts, “guerilla marketing tactics” and efforts to pressure MPs into voting against a Brexit deal once negotiations are complete so as to trigger either a second referendum or a general election to oust Prime Minister Theresa May’s Conservative government in favor of one led by hard-left Labor leader Jeremy Corbyn.

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Prime Minister Theresa May is under pressure over her handling of Brexit. (AP)

The revelation will serve to fuel fears from pro-Brexit Britons that there is an international campaign of elites from Brussels to London looking to quash the 2016 result. Nick Timothy, a former May chief of staff, said the news was a “wake-up call” to Brexiteers.

“Elitist Remainers are plotting to bring down the government,” he wrote.

Former U.K. Independence Party leader Nigel Farage made a similar call, saying he was glad Britain was finally talking about the influence of Soros, tweeting: “Time to wake up.”

Unease has been growing among the Brexit camp after the euphoria of the summer of 2016 has died down. The government’s negotiations with Brussels have become increasingly rocky, with the E.U. taking a hard line as negotiations heat up ahead of Britain’s departure from the bloc in 2019.

E.U. officials have likely been buoyed by increasingly vocal pro-Remain sentiment among Britain's political and media elites.

Former Prime Minister Tony Blair, who has been unapologetic in his calls for Britain to stay in the bloc, has been among the many high-profile voices calling for a potential second referendum, describing it not as an exercise in frustrating the will of the voters, but a chance for voters to “think again” once the terms of the deal are set.

PRO-EU ELITES TRY TO MAKE BRITS VOTE AGAIN ON BREXIT AS 'DIVORCE' TALKS HEAT UP

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Former Prime Minister Tony Blair has called for a Brexit do-over. (Reuters)

“Once we know the alternative, we should be entitled to think again, either through Parliament or an election or through a fresh referendum, which will, of course, not be a rerun of the first because it will involve this time a choice based on knowledge of the alternative to existing E.U. membership,” he wrote in a piece for The New Statesman last month.

But while some polls have suggested that Brits may be open to thinking again, others say the opposite. Leaders on both sides of the fight seem to acknowledge that the mood in the U.K. is that the government should see through the referendum.

“[P]ublic opinion remains consistent,” Timothy said in an analysis for the Telegraph. “There has been no sudden movement against Brexit, despite an ongoing campaign against it and criticism of the government’s negotiating position."

“I think people are changing their minds,” the pro-Remain Malloch-Brown said in a BBC interview last month, before conceding that “they haven’t changed it as dramatically as I would like to see.”