The Arron Banks debacle is a threat to our democracy – and it’ll happen again if authorities don’t act soon

After the National Crime Agency (NCA) opened an investigation into allegations about Arron Banks’ £8m donation to the pro-Brexit Leave.EU campaign he cofounded, he promised to clear up the matter by appearing on the BBC’s Andrew Marr Show on Sunday. In the event, his interview generated more heat than light.

The independent Electoral Commission said last week that a “number of criminal offences may have been committed”, adding there were reasonable grounds to suspect Mr Banks, a close ally of Nigel Farage, was “not the true source” of the donation.

Mr Banks told the programme that the biggest donation in British political history came from Rock Services, his UK-based insurance business, and not from Rock Holdings – which, as it is based offshore in the Isle of Man, would not have been permissible under electoral law. This appeared to contradict his own evidence to MPs that Rock Services was “just a service company”.

He dismissed speculation about foreign funding, saying “there was no Russian money, and no interference of any type”.

Characteristically, Mr Banks complained of a politically motivated “smear campaign” by Remainers to discredit and stop Brexit, blaming the commission, media organisations and MPs.

He is fond of such conspiracy theories. He is also happy to smear his critics; he used his wealth to write to every constituent of Damian Collins, Tory chairman of the Commons culture select committee, calling him a “snake in the grass”. Like the commission and the media, Mr Collins is doing his job without fear or favour, even if that means putting Mr Banks under the scrutiny he deserves.

Mr Banks, who strongly denies any wrongdoing, has welcomed the NCA investigation. Hopefully, bluster, diversionary tactics and obfuscation will cut no ice with the agency, and (unlike the commission) it will have the tools to get to the bottom of the allegations.

This inquiry matters. Leave.EU was not the official Brexit campaign, which fell to Vote Leave, led by Boris Johnson and Michael Gove. But Leave.EU’s financial clout allowed it to play an important part in the referendum. While keeping its distance from Mr Farage, Vote Leave was happy to reap the benefits of its nasty campaign on immigration, which included its infamous “breaking point” poster showing a queue of Syrian refugees.

The Banks investigation is about much more than Brexit. After evidence of Russian interference in elections, including the 2016 US presidential race, it is vital the UK authorities ensure that our democracy is not tarnished. If this has happened in the past, it must not happen in the future.

The government should take the culture committee’s warning that “democracy is at risk” much more seriously than it has done to date. It must urgently make a regulatory system designed for the analogue era fit for the digital age; bodies such as the Electoral Commission and the Information Commissioner need more powers and resources.

Unfortunately, the NCA inquiry is unlikely to be completed before the UK’s scheduled departure from the EU in March. In themselves, the allegations against Mr Banks do not warrant a rerun of the referendum or the Brexit process being paused, as some MPs argue. But they do add to the wealth of information that has come to light since 2016, and therefore strengthen the case for the voters to be given a Final Say on the Brexit deal Theresa May is expected to discuss with her cabinet on Tuesday. (In a bizarre twist, Mr Banks admits he would now vote Remain in protest at “corruption” in British politics and the government’s “sell-out” on Brexit).

The Independent’s Final Say campaign has also been bolstered by a call for a referendum by more than 70 business figures, who warn that the prospective agreement is “not nearly as good” as EU membership. This is a significant intervention, since businessmen and women often feel under pressure not to rock the government’s boat. Their views should be taken very seriously by MPs when they consider Ms May’s deal.