Brexit vote manipulated, says data whistleblower

"I think it is completely reasonable to say that there could have been a different outcome of the referendum had there not been, in my view, cheating," he said.

The revelations and accusations come almost exactly one year before the UK leaves the EU on 29 March, 2019.

Wylie said AIQ was subcontracted through Cambridge Analytica, a political data firm which is accused of manipulating voter behaviour to help Donald Trump win the US presidential election.

The comments follow separate accusations that the Leave campaign may have also broken electoral laws on spending thresholds, which are capped at £7m.

The Leave campaign spent £6.77m but then allegedly received a £625,000 donation from BeLeave, a youth group. The donation was then spent on AIQ services in breach of the £7m limit.

Wylie described the spending breach as part of a "common plan" coordinated by the pro-Brexit campaign.

"If this country is on the path of an irreversible decision, we really should be confident that the basis of that decision came from a free and fair vote - and what this evidence does is it calls into question whether it was free and fair," he said.

He said AIQ won the contract shortly after he met Vote Leave's campaign director, Dominic Cummings, in late 2015.

The over-spending allegations were made by Shahmir Sanni, a former Vote Leave volunteer, and revealed in a 50-page legal opinion released by the London-based Bindmands law firm.

The opinion claims Stephen Parkinson, who is prime minister Theresa May's political secretary, knew about the overspending and links between BeLeave and AIQ.

Parkinson was a key figure in the Vote Leave campaign and has since outed Sanni for being homosexual. Those revelations, says Sanni, has endangered some of his relatives in Pakistan.

Vote Leave officials have denied all the claims, noting that the British electoral commission has found no evidence of overspending. AIQ has denied any links to Cambridge Analytica as has Cambridge Analytica.

"Beyond an early-stage sales pitch to Vote Leave, Cambridge Analytica had no interaction with that group or any of their vendors," it said in a statement to the BBC.

Facebook CEO Mark Zuckerburg has also declined an invitation by the MPs to explain his firm's involvement in the scandal.