Leave campaigner Arron Banks is being investigated by the National Crime Agency for "suspected criminal offences" committed during the Brexit referendum.
The probe has been launched after the elections watchdog said it had reasonable grounds to suspect that Mr Banks was not the true source of £8 million worth of loans made during the campaign.
Leave.EU, co-founded by Mr Banks, its chief executive Elizabeth Bilney and the organisation that ran it, Better for the Country, are also being investigated by the NCA after a review carried out by the Electoral Commission.
Bob Posner, the Commission's director of political finance, said: "We have reasonable grounds to suspect money given to Better for the Country came from impermissible sources and that Mr Banks and Ms Bilney, the responsible person for Leave.EU, knowingly concealed the true circumstances under which this money was provided.
Read more:Arron Banks walks out of select committee for lunch with DUP MPs Ian Paisley and Sammy Wilson
"This is significant because at least £2.9m of this money was used to fund referendum spending and donations during the regulated period of the EU referendum.
"Our investigation has unveiled evidence that suggests criminal offences have been committed which fall beyond the remit of the Commission.
"This is why we have handed our evidence to the NCA to allow them to investigate and take any appropriate law enforcement action. This is now a criminal investigation.
"The financial transactions we have investigated include companies incorporated in Gibraltar and the Isle of Man. These jurisdictions are beyond the reach of the Electoral Commission for the purpose of obtaining information for use in criminal investigations or proceedings."
Read more:
- Arron Banks - Major Brexit campaigner admits he 'led people up the garden path'
- Everything you need to know about the Electoral Commission investigation into the Leave.EU campaign
