The facts about the NCA probe into the leave campaign and what it could mean for Brexit

The National Crime Agency is to investigate claims of criminal offences during the EU referendum by Arron Banks and his unofficial leave campaign. What could this development mean for Brexit?

What do we know so far?

Following a referral by the Election Commission, the NCA is to look into allegations that Banks was not, as he said, the source of £8m in funding given to the Leave.EU campaign.

It centres on claims that some of the money came via a company based in the Isle of Man and that Banks and his associates sought to cover this up. The Isle of Man is not part of the UK and so under election law could not be used as a source of funds during the referendum.

Those being investigated are Banks; Elizabeth Bilney, a long-time Banks associate who chaired the campaign; Leave.EU itself; Better for the Country, the company used to finance it; and “other associated companies and individuals”.

Banks and Bilney have vehemently rejected any wrongdoing, and said the investigation is motivated by political bias.

Is Russia connected to any of this?

There have been a series of reports, led by the Observer’s Carol Cadwalladr, about links between Banks and his campaign to Russia, prompting speculation about this being the source of some of the funding. However, neither the Electoral Commission nor the NCA have mentioned it as part of the inquiry.

Bilney also rejected the idea, telling the BBC: “I can confirm it wouldn’t have come from Russia … I run the group of companies where the money was from and we don’t have any transactions that are from Russia.”

What has been the reaction from remainers?

Several Labour MPs, among them Tottenham’s David Lammy, have called for the Brexit process to be paused pending the investigation and the Liberal Democrats said Brexit could not go ahead based on “a leave campaign littered with lies, deceit and allegations of much worse”.

Could the investigation halt or pause Brexit?

No. Aside from the difficult logistics involved, for example seeking an extension to article 50 while a potentially lengthy investigation takes place, there is no chance of Downing Street bowing to a demand which has not even been backed by the Labour party.

No 10 has rejected the idea of a pause, saying: “The referendum was the largest democratic exercise in this country’s history and the PM is getting on with delivering its result.”

Even if there were some proof of wrongdoing – and it must be stressed that so far there are only allegations – Brexiters could plausibly argue that there is no evidence that the £2.9m that was spent from the £8m would have had a decisive impact on the result.

The argument would be that Leave.EU was the unofficial campaign, and however much it spent, it was notably less than the £9m in taxpayers’ money spent by the government before the referendum so every household in England could receive a glossy 14-page pro-remain booklet.