Britain could have voted to stay in the EU without “cheating” by the official Vote Leave campaign, a whistleblower has told MPs in sensational evidence.

Christopher Wylie alleged that busting the legal spending limit allowed the campaign to win the support of enough voters through precisely targeted online advertising to have swayed the Brexit result.

Its data firm Aggregate IQ (AIQ) had a “significant” conversion rate of between 5 per cent and 7 per cent – and had told him it had targeted five to seven million people for the referendum.

“I think it is completely reasonable to say there could have been a different outcome of the referendum had there not been, in my view, cheating,” Mr Wylie told the inquiry.

The former director of research for scandal-hit Cambridge Analytica warned the full picture of what took place may not become clear until after Britain’s exit from the EU in March next year.

“What a shame it would be if we found out that there had been pervasive cheating in the referendum and Brexit has already happened and you can’t go back,” he told the Commons Digital, Culture, Media and Sport Committee.

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During a four-hour session, Mr Wylie also:

* Alleged that his predecessor died in suspicious circumstances in a Kenyan hotel after a “deal went sour” – and may have been poisoned

* Alleged AIQ distributed “incredibly threatening and violent” videos to intimidate voters in Nigeria, after the medical records and emails of a presidential candidate, Muhammadu Buhari, were hacked

* Claimed Vote Leave, a youth Brexit group called BeLeave, the Democratic Unionist Party (DUP) and Veterans for Britain were all working together in the campaign

* Described BeLeave – which received a donation of almost £680,000, allegedly used for Vote Leave – as effectively a money laundering vehicle

* Revealed his anger that two young people he introduced to Vote Leave – fellow whistleblower Shahmir Sanni and Darren Grimes – were exploited to break the law

* Said Alexander Nix, Cambridge Analytica’s chief executive was “very wealthy already”, adding: “There was one time when we were running late because he had to pick up a £200,000 chandelier”

Mr Wylie was called to give evidence after sparking an international outcry with his revelation that Cambridge Analytica harvested Facebook data from more than 50 million voters for Donald Trump’s election campaign.

Mr Sanni has alleged that Vote Leave used its links with BeLeave to get around the £7m referendum campaign spending limit imposed by the Electoral Commission.

A 50-page dossier of evidence has now been handed to the election watchdog, alongside a legal opinion that the campaign may have broken electoral law.

In his evidence, Mr Wylie said it was “weasel words” to claim AIQ was a separate entity to Cambridge Analytica, because it had been set up and worked within its auspices.

“This is a company that has worked with hacked material, this is a company that will send out videos of people being murdered to intimidate voters, this is a company that goes out and tries to illicitly acquire live internet browsing data of everyone in an entire country,” he said.

“I think a lot of questions should be asked about the role of AIQ in this election and whether they were indeed compliant with the law here.”

On the Nigeria campaign, he added: “AIQ was handed material in Nigeria from Cambridge Analytica to distribute online.

“That’s distribution of kompromat and of incredibly threatening and violent video content which I’ve passed on to the committee.

“The videos that AIQ distributed in Nigeria with the sole intent of intimidating voters included content where people were being dismembered, where people were having their throats cut and bled to death in a ditch, they were being burned alive.