Shahmir Sanni was a volunteer for Vote Leave and explained how he was a Brexiteer through and through.
However he has compiled The Cambridge Analytica Files, which detail how he believes the anti-EU campaign was actually breaking the rules.
He claims Vote Leave “coordinated” their budgets with BeLeave and thus gained an extra £625,000 on the whopping £7million budget.
Shahmir told hosts Richard Madeley and Susanna Reid on Good Morning Britain: “Today we’ve compiled a 40-page documents and we’re presenting it for the Prime Minister.
“All the lawyers believe that it is [compelling evidence].
“I’ve gone out of my way to make sure the public can see it themselves.”
But Richard hit out at the whistleblower, asking: “But do you think it made any difference? Do you think what you are alleging made any difference to the vote?”
Knocked back by the question, the whistleblower: “Of course I do.”
Suzanne then jumped in and said: “Considering Vote Leave had a £7million budget, did the £625,000 you are alleging was illegally spent, would that have had a material affect on the referendum?”
Shahmir said: “Leave won by two percent and £625,000 is more than enough to get you hundreds of millions, even billions of impressions on your advert. It’s a digital campaign which means millions were seeing the content again and again.”
Richard then said: “Would you go so far as saying if this hadn’t happened Remain might have won?”
But Shahmir responded: “That’s not my place to say.”
Richard demanded to know what Shahmir was getting out of publishing such explosive accusations to which he said: “Nothing.
“I’ve gone through a gruelling process of just trying to understand what went wrong.
“As a Brexiteer myself it’s important that the public see what went on.”
Shahmir added: “The only thing I’m doing is facilitating and providing evidence.
“I was pleased with the result I was elated – Brexit was my first political campaign.”
Former head of BeLeave, Darren Grimes, denied the allegations, calling them “damaging” and “untrue”.
Boris Johnson tweeted over the weekend: “Observer/C4 story utterly ludicrous, #VoteLeave won fair & square – and legally.
“We are learning the EU in a year and going global #TakeBackControl.
Dominic Cummings of Vote Leave strongly denied the claims and Chief Brexit Negotiator, David Davis added: “It is the job of the commission, not ministers, to make a judgement.”
Good Morning Britain airs weekdays on ITV from 6am.