By Guy Faulconbridge and Andrew MacAskill
LONDON (Reuters) - Britain's serious crime agency began an investigation on Thursday into Brexit backer Arron Banks and one of the main groups that campaigned to leave the European Union over the true source of millions of pounds in loans.
Separately, the Electoral Commission said it had found serious offences in the funding of the Leave.EU campaign since the 2016 Brexit referendum, including loans from impermissible donors and the concealment of financial transactions.
The investigation is sensitive because it could potentially cast doubt on the legitimacy of the vote.
The Commission said it suspected criminal offences had been committed and that Banks was not the true source of 8 million pounds in loans to the Brexit campaign groups.
Announcing the inquiry, the National Crime Agency (NCA) - which usually focuses on tackling serious and organised crime - said its involvement was due to offences other than breaking electoral law.
Banks, who was pictured with Donald Trump and leading Brexiteer Nigel Farage outside a gilded elevator soon after Trump’s 2016 U.S. presidential election victory, said he welcomed the inquiry.
"We welcome this investigation as it is an opportunity for us to clear up the matter," Banks told Reuters.
In the June 23, 2016 referendum, 17.4 million voters, or 51.9 percent, backed leaving the EU while 16.1 million, or 48.1 percent, backed staying.
Opponents have repeatedly called for a rerun of the vote, alleging financial improprieties in the Brexit campaign and possible foreign - or even Russian - funding for the campaign. Britain is due to leave on March 29, 2019.
British Prime Minister Theresa May's spokeswoman refused to comment on the investigation but said the government had so far not seen any successful interference in Britain's democratic processes but it remained vigilant.
"To date, we have not seen successful interference in UK democratic processes," the spokeswoman said.
Banks said he had written to May to ask for an investigation, and accused the Electoral Commission of being opposed to Brexit.
Helen Hayes, a lawmaker in the opposition Labour Party, called for Brexit to be halted while the NCA carried out the investigation. "The government cannot and must not continue blindly towards the constitutional & economic precipice of Brexit while such serious allegations of the undermining of our democracy remain," she said on Twitter.
LOANS FOR BREXIT?
Supporters of Brexit dismiss speculation that foreign, including Russian money, was used in the campaign, saying that attempts to stop Brexit would thrust Britain into a grave political crisis.
The Electoral Commission said some loans made to Leave.EU and Better for the Country Limited (BFTCL) in 2015 and 2016 by the Isle of Man-incorporated Rock Holdings Limited were impermissible.
It said Banks, Elizabeth Bilney and others in the campaign concealed the true details of financial transactions.
"Rock Holdings is a company I own and control and I'm a U.K. taxpayer, no Russian or foreign money has ever come into it," Banks told Reuters.
Before the referendum, Banks financed Leave.EU, a campaign led by Farage who was then the leader of the UK Independence Party.
Banks has repeatedly dismissed questions about the source of his own wealth. He owns a successful insurance business and previously made donations to the Conservative Party.
"In our analysis, Rock Services' then and historic profits were not sufficient to enable it to have funded the 8 million pounds," the Electoral Commission said, adding that it suspected the company did not fund the payment from its UK income as required by electoral law.
(Editing by Stephen Addison and Matthew Mpoke Bigg)