Amid Brexit uncertainty and allegations, UK lawmakers consider Mueller-like inquiry It's been three years since the Brexit referendum, and serious questions remain.

The 448-page, comprehensive and controversial Mueller report was released this month after nearly two years -- and Americans are arguably left with more questions than answers.

Across the pond, a similarly drawn out and complicated affair -- involving a dissatisfied electorate looking for an "anti-establishment" solution, allegations of criminal behavior and Russian interference into high stakes politics -- led to its own political upheaval, and perhaps just as much uncertainty.

The parallels between Russian meddling in the U.S. presidential election and the Brexit referendum in Britain are striking. In fact, calls among lawmakers have been growing for a public inquiry, according to The Guardian, into Prime Minister Theresa May's Brexit strategy.

Three years after the referendum, the country remains unclear about how it will proceed, leading some politicians to advocate for a Mueller-style probe into illegalities -- some alleged, some proven -- into the campaign itself.

The whistleblower and the $800,000 payment

In 2015, then-Prime Minister David Cameron decided that the U.K. would hold a referendum on the U.K.’s membership in the European Union, the trading and political bloc that binds Europe together. The answer on the ballot of the referendum, held in June 2016, was simple: leave or remain.

That's when things got really murky.

The Electoral Commission, the organization that oversees the U.K.’s democratic process, decreed that there would be only one officially designated campaign each for both sides. The official Remain campaign, supported by Cameron’s government as well as the opposition Labour Party, was called Britain Stronger in Europe.

Official designation meant a campaign spending limit of $9.8 million.

On the Leave side, however, there was a split. Two major advocacy groups, named Vote Leave and Leave.EU, competed for official designation. The Electoral Commission ultimately awarded Vote Leave with the official designation.

That’s where Shahmir Sanni comes in.

A young Vote Leave staffer who joined in May 2016 as a volunteer, Sanni designed ads for BeLeave, a separate organization that worked closely with the campaign. Its ads were widely disseminated on social media by Aggregate IQ (AIQ), a Canadian technology firm that targeted potential voters based on how receptive they would be to Brexit campaigning.

The technique is known as “micro-targeting” because campaigners are able to send messages tailored to specific groups of voters based on demographic information and their interests, according to the commission. The tactic was similar to what was later used in the Trump election campaign.

The U.K.’s 2018 inquiry into so-called fake news found that AIQ had a “close working relationship” with Cambridge Analytica, owned by hedge fund billionaire Robert Mercer and headed by Steve Bannon, who worked for Trump during the 2016 presidential election campaign.

The inquiry did say that this stopped short of sharing data.

Cambridge Analytica has been accused of using personal information from 50 million Facebook users without consent to build a system to profile U.S. voters to target them with personal advertisements. Its parent company, SCL, went bust after the revelations, which it denies.

Back in the U.K., AIQ’s role was crucial, Sanni says. It was not just the typical campaigning of the referendum -- promises of more money for the health service and the now infamous slogan imploring voters to “Take Back Control” from the EU -- but the ads were specifically designed to address “what the data was saying would be most effective.”

This advertising was “highly influential in the final result,” Mike Harris, CEO of 89up, a social media analytics firm, told ABC News.

As the campaigning drew to a close, however, Vote Leave was running out of money. Its $9.8 million had been nearly wholly spent, so to circumvent campaign spending laws, Vote Leave made a $807,000 payment to BeLeave in early June 2016.

It never saw the money, though.

“At the time [the Vote Leave lawyers] were the ones telling us that everything was fine,” Sanni said. “When we got the big chunk of money it went straight to AIQ. We never touched it.”

That sum was used to ramp up the social media advertising on which Vote Leave’s tactics hinged. Sanni went to the Observer, and speaking on the record to the journalist Carole Cadwalladr, blew the whistle on Vote Leave’s malfeasance in March, 2018, nearly two years after Vote Leave won the referendum.

The evidence is that Moscow cannot significantly influence the outcome of votes, from Brexit to the U.S. presidential elections.

“I didn’t want to have that on my conscience,” he told ABC News. “I could very easily have stayed quiet and had a very successful career in British politics.

"But I’d rather not live my life knowing that I had partaken in a crime,” added Sanni, who is now calling for a public inquiry into the electoral malfeasance of the referendum.

In July 2018, the Electoral Commission found Vote Leave guilty of breaking electoral law and referred the case to the police, which specifically cited Sanni’s allegations.

Vote Leave appealed the judgement, but on March 29, 2019, it dropped its appeal. The commission found Vote Leave guilty of “multiple offences under electoral law.”

It was fined $79,000.

The ‘Bad Boy of Brexit’: From Russia with gold?

One of the key findings of the Mueller report was that, although collusion with the Trump campaign could not be proven, Russia actively sought to influence the U.S. election in a number of ways. The same strategies were employed in the U.K., mainly through Russian bot farms.

The more than 150,000 Russian social media accounts that posted pro-Brexit messages just before the referendum, according to U.K. Parliament’s report into “Disinformation and fake news,” is just one example.

Far more insidious, though as yet unproven, are the allegations against Arron Banks, the millionaire businessman who co-founded the largest unofficial Brexit campaign, Leave.EU, and Nigel Farage, the lifelong Brexit campaigner who may be more familiar with U.S. audiences.

Both men were pictured alongside Donald Trump after his election victory in 2016.

Banks, an insurance entrepreneur, was largely unknown in the U.K. before he put up $10.3 million to launch Leave.EU and other Brexit organizations prior to the 2016 referendum. According to the lawmaker Damian Collins, this is the “largest political donation” in British political history.

Yet doubts persist around the source of that money, with allegations speculating that the money could have Russian roots. Banks’ own estimates of his net worth vary, due to the diversity of his business interests, but he told the Financial Times in 2015 that he was worth $130 million. However, an investigation by Open Democracy found that Banks’ gross earnings since 2001 stood at only $32 million.

How Banks could afford his generous donations remains a “mystery,” according to the report.

The Electoral Commission has referred Banks and Leave.EU to the National Crime Agency (NCA), the U.K.’s leading organization against organized and economic crime, which is now investigating the matter. A spokesperson for the NCA said it “will report the outcome of the investigation at the earliest opportunity.”

One theory of the source of the donation comes from Banks’ business interests in Russia, which he has repeatedly denied. The U.K.’s inquiry into “Disinformation and 'fake news,'” published by the Department for Culture, Media and Sport, also says “Banks had many meetings with Russian officials, including the Russian Ambassador, Alexander Yakovenko, between 2015 and 2017.”

The Parliament committee that issued the report concluded Banks and his lawyer, Andy Wigmore, had “misled” it on how many meetings had taken place. They “walked out” of the evidence session, the report found, to “avoid scrutiny” as to the nature of those meetings.

Banks himself was featured in the special counsel report. Mueller and Democrats from the House Intelligence Committee took a “special interest” in Banks during the inquiry, according to the New York Times.

Farage was featured on page 55 of the final report in general terms, with mention of a potential meeting between Jerome Corsi and Julian Assange, which never happened.

Wigmore, Banks’ lawyer, vehemently denied the allegations as “bollocks” in an interview with ABC News. He adds that they have fully co-operated with the NCA and look forward to being exonerated.

“If everyone's trying to undermine Brexit by saying the person that gave the biggest donation acted illegally and was a puppet for Putin, of course it's delicious for the press,” he told ABC News. “Why wouldn't you? [But] the facts are actually quite boring.”

Meetings with Russian ambassadors are the usual course when looking into business, he claims.

“There was just some discussions of Brexit in politics, but not like we had any deep knowledge other than from our perspective of what was going on,” he added.

Why no inquiry?

Despite the depth and breadth of the allegations against the Brexit campaign, no Mueller-style inquiry has been forthcoming. The most likely form this would take in the U.K. would be a public inquiry, with various actors called to account in public at committees held in the House of Commons.

There is arguably a bigger story, however, one that has implications across both sides of the Atlantic, of political camps increasingly divided. This can be seen in the U.S. in terms of the reaction to the Mueller report -- one side claiming total vindication, the other considering whether to initiate impeachment proceedings.

In the U.K., the nation remains split down Brexit and Remain lines. A study commissioned by the think tank "The U.K. in a Changing Europe" found that Britons increasingly identify with how they voted in the Brexit referendum.

In total, the Electoral Commission found that Remain campaigns outspent Leave by approximately $7.5 million.

Not all are convinced, however, that a public inquiry is even necessary.

“I wouldn't use the term hysteria but I think some of the complaints about Leave campaign wrongdoing are over the top,” John Rentoul, the Independent’s chief political commentator, told ABC News.

Mark Galeotti, an expert on Russia, also believes the concrete influence of the Kremlin in western elections has been “massively” overstated.

“The evidence is that Moscow cannot significantly influence the outcome of votes, from Brexit to the U.S. presidential elections,” he told ABC News.

Whatever the answer, the story is far from over. Britain’s exit from the EU has been delayed once again, this time to October 31.

A Mueller-style inquiry into the Brexit vote may not be in the works for the near future. But it seems the currents now moving beneath the democratic process in the West -- particularly new techniques of social media campaigning and Russian interference -- are not going anywhere.