MILLIONAIRE Brexit backer Arron Banks has dismissed claims he was financed by Russia as a “piece of nonsense”.

It comes as a Labour MP has called on the government to investigate the possibility that the Kremlin interfered in the EU referendum.

The Open Democracy website reported that Banks, who donated around £9million to pro-Brexit groups — making him one of the largest single donors in British political history — had suffered setbacks in business in 2013 and was in financial difficulty. His underwriting business Southern Rock was under scrutiny from financial regulators in Gibraltar and had reserves below what was required.

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However, according to the site, “a year later, these financial worries seem to have completely evaporated. Banks had begun buying diamond mines, investing millions into chemical companies and wealth management firms, setting up loss-making political consultancies, and most famous of all — funding Ukip.”

The article adds: “One question remains though. If Banks was in such a tight spot in September 2013, how did he manage to be so generous the following year?”

Much of Banks’s wealth is held in offshore jurisdictions including Belize, the Isle of Man, the British Virgin Islands and Gibraltar, making it hard to asses just how wealthy he is, and pen Democracy accepts his money could be legitimate.

Banks is married to Ekaterina Paderina, the daughter of a Russian state official, who has previously been accused of being a spy.

On Thursday MP Ben Bradshaw told the Commons there were “questions” over “the real wealth of Arron Banks, the main financial backer of Leave.EU.”

He asked that the Government and the Electoral Commission examine the reports carefully, “given the widespread public concern about foreign, particularly Russian, interference in western democracies”.

In a statement, Banks said: “Just like Crooked Hillary, Bradshaw still fails to understand why his side lost, and thus continues to peddle this rather tedious myth of a Russian conspiracy. Sad!”

The Russian Embassy in London told The National: “Russia is not and was not involved in any election/referendum campaigns in UK. They are Britain’s internal matter.”