Brexit campaigner Arron Banks has been referred to the National Crime Agency by the Electoral Commission for suspected criminal offences during the EU referendum.

An investigation by the elections watchdog into £2m purportedly loaned and £6m purportedly donated by Banks to Better for the Country – the company that ran the Leave.EU campaign – has found “reasonable grounds” to suspect that he was not the true source of the money.

Of the £8m in question, £2.9m was spent during the referendum campaign, when expenditure was subject to strict regulations. Bob Posner, the Commission’s legal counsel, said the watchdog suspected that Banks and Elizabeth Bilney, another director of Better for the Country, had “knowingly concealed” the true source of the money.

“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,” he stated. “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.” The National Crime Agency has said it is investigating Banks despite electoral law offences not usually falling under its remit because of the “potential for offences to have been committed other than under electoral law.”

Both Banks and his Leave.EU sidekick Andy Wigmore have denied any allegations of criminality. “We’re pleased it has been referred because we can finally now put to bed these ludicrous allegations,” Wigmore said.

Pro-EU politicians have – as was inevitable – reacted to the news with demands for Brexit to be stopped. A classic of the genre comes from David Lammy, the Labour MP for Tottenham, who tweeted: “Brexit must be put on hold until we know the extent of these crimes against our democracy.”

The problem with this argument, and indeed for anyone hoping that news of a criminal investigation into Banks could reverse the outcome of the referendum, is that at present the only legal certainty in all of this is that the United Kingdom is leaving the European Union on 29 March 2019.

The likelihood that any investigation or subsequent legal proceedings that may follow will be resolved by then is non-existent, as the slow progress of the still ongoing police investigations into separate allegations over the conduct of Leave campaigners referred by the Commission in May and July shows. For those still indulging the forlorn hope of stopping Brexit, this development is no help.