LONDON • A whistle-blower at the heart of a Facebook data scandal has said the Brexit referendum could have gone the other way if rules had not been broken during the campaign.

"I think it is completely reasonable to say that there could've been a different outcome in the referendum if there hadn't been, in my view, cheating," said Mr Christopher Wylie, a former contractor at political consultancy Cambridge Analytica.

He was giving evidence to a parliamentary committee that is investigating allegations that information on millions of Facebook users was scooped up without their consent. Brexit campaigners have denied any wrongdoing.

According to earlier news reports, Cambridge University researcher Aleksandr Kogan created a personality analysis app that was used by 270,000 Facebook users, who in turn gave the app permission to access data about themselves and their friends - ultimately exposing a network of 50 million people.

Mr Wylie also contradicted remarks made by Cambridge Analytica chief executive Alexander Nix to the committee. He said: "I think Nix's comments to your committee were misleading and dishonest.

"It is categorically untrue that Cambridge Analytica has never used Facebook data. Facebook data and the acquisition using Aleksandr Kogan's app was the foundational data set of the company. That's how the algorithms were developed."

Cambridge Analytica immediately denied the claims on Twitter.

"No company would risk basing their core offering on illegal data," it wrote. "We engaged Dr Kogan in good faith, and deleted his company's data once we knew we had to. We've already certified this to Facebook," it added.

Cambridge Analytica has been under pressure since it was found to have held vast swathes of Facebook user data after obtaining it from Mr Kogan, who then shared the data without the social network's permission.

Mr Kogan has previously said he was being used "as a scapegoat" in the scandal, and that he believed he was handling the data he acquired "appropriately". Mr Wylie said he had passed evidence to the committee about the firm's involvement with Canadian company Aggregate IQ Data Services, which he said was paid hundreds of thousands of pounds by Cambridge Analytica as part of its work for a lobby group during the 2016 referendum.

Mr Damian Collins, the head of the parliamentary body questioning Mr Wylie, said the committee will publish its findings from today.

Meanwhile, Facebook yesterday said its chief executive Mark Zuckerberg will not appear before the same lawmakers to give evidence, despite a renewed demand to have him do so. Mr Zuckerberg, in response to an earlier request, offered to send one of his deputies.

Mr Collins said the seriousness of the allegations meant it was "appropriate" for Mr Zuckerberg himself to offer an explanation, whether in person or via video-link.

His comments came amid renewed pressure from the European Union to disclose more details about how the data of up to 50 million users is alleged to have been taken from Facebook, and used in political campaigns.

The EU has given the social media giant two weeks to answer queries over the scandal, which has heavily hit Facebook's share price, and raised major questions over how social media firms use private data.

Mr Zuckerberg last week apologised for Facebook's failure to protect its users. The company reinforced this message by taking out full-page advertisements in British and United States newspapers.

BLOOMBERG, AGENCE FRANCE-PRESSE