An investigation has been launched into whether major Leave funder Arron Banks breached rules during the EU referendum campaign.
The Electoral Commission announced it is looking at whether or not multi-millionaire Mr Banks breached finance rules in relation to donations or loans made to campaigners before the Brexit vote.
Their investigation will also probe the activities of a firm called Better for the Country Limited (BFTCL), of which Mr Banks is a director.
Bob Posner, the Electoral Commission's director of political finance and regulation and legal counsel, said: "Interest in the funding of the EU referendum campaigns remains widespread.
"Questions over the legitimacy of funding provided to campaigners at the referendum risks causing harm to voters' confidence.
"It is therefore in the public interest that the Electoral Commission seeks to ascertain whether or not impermissible donations were given to referendum campaigners and if any other related offences have taken place."
In response to the investigation, Mr Banks posted on Twitter: "Gosh I'm terrified."