Christopher Wylie hearing: Cambridge Analytica whistleblower to give evidence to US Congress over Facebook data breach

A former employee of Cambridge Analytica who claims the firm used the personal data of tens of millions of Facebook profiles to allegedly help Donald Trump’s election campaign, is to testify before US Congress.

Christopher Wylie said he had accepted an invitation to give evidence to the US House Intelligence Committee and House Judiciary Committee this week.

He disclosed last month that the political consultancy firm had harvested data from users of the social media site by using personality quizzes to build up psychological profiles.

As the US election approached, he said it then used this data to target them with bespoke political advertising.

His revelations triggered investigations in the UK and US. Facebook founder Mark Zuckerberg was grilled over the scandal by senators earlier this month.

Mr Wylie was invited to give evidence by Democrat Adam Schiff, a ranking member of the House Intelligence Committee.

In a letter to Mr Wylie and his lawyer, the California politician said that if his "account and documentation is accurate, this misappropriation of private data is a serious invasion of the privacy interests of the American people by Cambridge Analytica and potentially other individuals and entities."

He added that his revelations raised “important questions about Cambridge Analytica’s activities on behalf of then-candidate Donald Trump’s campaign during the 2016 US elections, the specific roles of persons of interest, including Steve Bannon and Robert and Rebekah Mercer, as well as the firm’s ties to Russia.”

Mr Bannon was a vice-president of Cambridge Analytica’s board before becoming chief executive of Mr Trump’s campaign.

Billionaire Mr Mercer and his daughter Rebekah were major donors to the campaign and investors in the firm.

Mr Schiff said Mr Wylie’s revelations also raised “serious questions about the veracity of the testimony” given to the House Intelligence Committee by now-suspended Cambridge Analytica chief executive Alexander Nix last year.

Mr Nix was questioned by the committee was part of its investigation into alleged Russian interference in the presidential election campaign.

He later told an uncover Channel 4 News reporter that Republican members asked him just three questions.

“After five minutes – done,” he said. “They’re politicians, they’re not technical. They don’t understand how it works.”

Mr Zuckberg was also widely deemed to have faced easy questions when he testified before the House Committee on Energy and Commerce.

Following Mr Wylie’s revelations, Democrats have been pushing for Mr Nix to be summoned to give further testimony.

Since the scandal erupted, Cambridge Analytic has insisted Mr Trump’s team did not use its data and said it only “provided limited staffing”.

But in the Channel 4 News footage, Mr Nix chief boasted that his firm worked on “all” the elements of the Republican’s campaign.

“We did all the research, all the data, all the analytics, all the targeting, we ran all the digital campaign, the television campaign and our data informed all the strategy,” he said.

Mr Wylie will give evidence to the Judiciary Committee in private on Tuesday and to the Intelligence Committee in public on Wednesday.

“Democracies around the world are under threat from malicious actors who seek to use social media as an information battleground,” he said. ”We must take this seriously.”

He gave evidence to British MPs on the Digital, Culture, Media and Sport Committee last month, when he alleged online advertising “cheating” may have swung the EU referendum in Vote Leave’s favour.