Billionaire investor George Soros gave £400,000 to an anti-Brexit group, founded by Remainer Gina Miller, in the wake of last year's UK General Election, it has been revealed.
Soros donated to the Best for Britain group, which Miller set up to bring legal action against the government to gain parliament's consent before starting negotiations to leave the European Union.
He is also said to have hosted a dinner for Conservative donors at his London home last week to discuss the issue, according to Financial Times sources.
Soros's Open Society Foundation said it has also donated a total of £303,000 to other pro-EU groups such as the European Movement UK, Scientists for EU and think-tank Bright Blue for its work on protecting European rights.
However, Miller denied links with the billionaire as she revealed she had left Best for Britain, and criticised the group for being "undemocratic" by not disclosing its financial backers.
She released a statement which said: "Contrary to misleading media reports, I have absolutely no relationship with, or involvement in the work of, Best for Britain.
"One of the greatest failures, and sadnesses, of the whole Brexit era has been the lack of transparency about key players' motivations, agendas and activities and incompleteness of information that is placed in the public domain.
"I encourage Best for Britain, and all those keen to play their part in the Brexit debate, to be open and honest about what they stand for, whom they represent and by whom they are funded."
Miller, who is also a high-profile campaigner for transparency in fund fees, is also preparing a dossier to present to the Financial Conduct Authority to show instances where the recently introduced MiFID II rules have been contravened by investment firms, as they are not complying with fee transparency rules, and said she will pursue legal action against the regulator if it does not give more specific guidance, according to City AM.