The National Crime Agency has announced that it has ended its investigation into a series of concerns raised by the Electoral Commission about the activities of Brexit bankroller Arron Banks.

The NCA said it found “no evidence” that criminal offences were committed under the Political Parties, Elections and Referendums Act 2000 (PPERA) or under company law by any of the individuals or organisations referred to it by the Electoral Commission, which included Arron Banks, his Leave.EU Chief Executive Liz Bilney and their pro-Brexit campaigns Better for the Country Ltd and Leave.EU.

The NCA added that it “neither confirms nor denies” that it is investigating separate media reports alleging that Mr Banks has been involved in other criminality related to business dealings overseas.

In a statement published yesterday, the NCA declared that Banks took a £6m loan to fund his Brexit campaigning from his company Rock Holdings Ltd, which is based outside the UK in the Isle of Man.

Asked last year by the BBC”s Andrew Marr whether his donations to Leave.EU were “connected in any way” to Rock Holdings Ltd, Banks said “no, absolutely not”. Yesterday, the NCA stated that “Mr Banks took a loan from Rock Holdings Ltd”. However, the NCA concluded that “Mr Banks was legally entitled, in his capacity as an individual, to release these funds”.

The NCA also stated that it has “not received any evidence to suggest that Mr Banks and his companies received funding from any third party to fund the loans, or that he acted as an agent on behalf of a third party.”

Writing on Twitter after the decision, Banks said: “No overseas money was used in the Brexit campaign, it was my money. We intend to issue a claim against the EC for the decision to refer this matter to the @NCA publicly. We calculate the losses well over £10million”.

Responding to the NCA’s statement, an Electoral Commission spokesperson said: “We are concerned about the apparent weakness in the law, highlighted by this investigation outcome, which allows overseas funds into UK politics. We have made recommendations that would tighten the rules on campaign funding and deter breaches. We urge the UK’s governments to act on those recommendations to support voter confidence.”

The NCA’s finding does not affect a previous Electoral Commission decision to fine Banks and Leave.EU for a number of breaches of electoral law, including overspending. It also does not affect a separate ruling by the Information Commissioner that Leave.EU and Banks’s insurance firm Eldon breached data protection laws, for which they were fined a total of £120,000 earlier this year.

openDemocracy has previously reported that Arron Banks misled parliament about political work carried out by staff at his insurance company, and misled both parliament and the UK Information Commissioner about his contact with the controversial Trump-linked firm, Cambridge Analytica.

The NCA decision comes after Brexit activist Darren Grimes in July won his appeal against a £20,000 Electoral Commission fine, imposed after the regulator found he had broken electoral law during the Brexit referendum. In that case, the judge ruled that the Electoral Commission had set too high a threshold for determining whether Grimes’s campaign group, BeLeave, was correctly registered – and further ruled that even if Grimes had committed the offence, the fine imposed was too high.

After the judgement, Grimes attacked the Commission’s handling of the case, speaking of “huge toll” it had taken on him and his family, and saying that the case involved “incorrectly ticking a box on a form”.

Separately the Vote Leave campaign, led by Boris Johnson and Michael Gove, withdrew their appeal against a £61,000 fine imposed by the Commission for multiple instances of breaking electoral law in March. Vote Leave is understood to be seeking a judicial review of the Electoral Commission’s decision to make its report into Vote Leave public, with a hearing scheduled for October.

Last month the Metropolitan Police also confirmed they would be taking no further action to investigate Banks’s Leave.EU. They said they are continuing to pursue an investigation into the activities of Vote Leave.

Speaking in reaction to the NCA decision on Arron Banks and Leave.EU yesterday, Steve Goodrich at Transparency International said: “It has been clear for some time that the rules on company political donations provide weak protection against funds from overseas. But the interpretation taken by law enforcement in this case make it non-existent. With a general election on the horizon, those seeking to distort our political process will take comfort they can intervene without consequence. Parliament needs to clarify the intent of the rules on company donations urgently to close this gaping loophole in the law.”

On Twitter, Leave.EU CEO Liz Bilney accused the Electoral Commission of being “Remain biased” and claimed the criminal investigations into her and Banks had been fuelled by Remain-backing MPs "desperately trying to overturn the result of the referendum".