A Cambridge Analytica whistleblower has suggested Facebook uses people's mobile phones to spy on them at home or at work.

Christopher Wylie, a former employee of the scandal-hit firm, said companies like Facebook use the microphone on mobile phones to help tailor their adverts.

He told a Commons committee yesterday he believes the social media giant is able to decipher whether someone is out in a crowd of people, in the office or at home.

Christopher Wylie (pictured), a former employee of scandal-hit firm Cambridge Analytica, said companies like Facebook use the microphone on mobile phones to help tailor their adverts

Asked by Conservative MP Damian Collins (pictured) whether Facebook can listen to what people are saying to shape their advertising, Mr Wylie said they use the smartphone app microphone for 'environmental purposes'

Asked by Conservative MP Damian Collins whether Facebook can listen to what people are saying to shape their advertising, Mr Wylie said: 'On a comment about using audio and processing audio, you can use it for, my understanding generally of how companies use it... not just Facebook, but generally other apps that pull audio, is for environmental context.

'So if, for example, you have a television playing versus if you're in a busy place with a lot of people talking versus a work environment.'

'It's not to say they're listening to what you're saying. It's not natural language processing. That would be hard to scale.

'But to understand the environmental context of where you are to improve the contextual value of the ad itself' is possible.'

Mr Wylie was answering questions on Cambridge Analytica's influence over the Brexit referendum result. Pictured: House of Commmons Digital, Culture, Media and Sport Committee's inquiry into Fake News yesterday

Mr Collins's question about Facebook spying is reflected in research carried out by Internet charity DotEveryone.

Their studies show seven per cent of people think Facebook listens to their phone conversations and five per cent believe it is capable of tracking their eye movements when they're looking at a screen.

Mr Wylie's claims were only speculative and said Mr Collins's was 'probably one for Facebook'.

The tech giant has long denied allegations of spying on people to customise ads.

But since it was revealed it harvested data from over 50 million users to aid Cambridge Analytica's election campaigns, other data issues have been brought into question.

Rob Goldman, vice president of ad products at Facebook directly addressed the claims on Twitter in October last year.

Rob Goldman, vice president of ad products at Facebook directly addressed the claims on Twitter in October last year saying the social media giant doesn't use the microphone for ads. Pictured: Founder Mark Zuckerberg

He wrote: 'I run ads product at Facebook. We don't - and have never - used your microphone for ads. Just not true.'

'That includes Facebook-owned Instagram.'

A Facebook spokesman told MailOnline it does not use phone microphones for ads, instead using interests and other profile information to shape what users see on their News Feed.

Any third party seeking permission to use phone microphones would have to obtain it independently from the user, they added.

Mr Wylie was answering questions on Cambridge Analytica's influence over the Brexit referendum result.

In previous sessions at the House of Commons the former CA employee has made claims his predecessor was found dead under 'suspicious circumstances' in Kenya.

He said Dan Muresan was working for President Uhuru Kenyatta's re-election campaign when he was found dead in 2012 amid reports a deal he was working on went 'sour'.

Giving evidence to the culture select committee of MPs, Mr Wylie told how rumours that Mr Muresan had been killed circulated around the controversial data firm.

And he heard talk the Kenyan police had been bribed not to enter the hotel room for 24 hours in a bid to cover up the possible murder.

Cambridge Analytica tweeted yesterday to refute Mr Wylie's extraordinary claims.

A spokesman wrote: 'Christopher Wylie was a part-time contractor who left in July 2014 and has no direct knowledge of our work or practices since that date.'