Facebook allowed the Obama campaign to access the personal data of users during the 2012 campaign because they supported the Democratic candidate according to a high ranking staffer.

Carol Davidsen, who worked as the media director at Obama for America and has spoken about this in the past, explained on Twitter that she and her team were able to ingest massive amounts of information from the social network after getting permission from Facebook users to access their list of friends.

'Facebook was surprised we were able to suck out the whole social graph, but they didn't stop us once they realized that was what we were doing,' wrote Davidsen.

Carol Davidsen, (left) who worked as the media director at Obama for America, claims Facebook allowed them to mine American users' profiles in 2012 because they were supportive of the Democrats

US President Barack Obama on the campaign trail in 2012 - when the mining allegedly occurred

She wrote that, not only did Facebook not try to stop them, but the company said they'd made a special exception for them.

'They came to office in the days following election recruiting & were very candid that they allowed us to do things they wouldn't have allowed someone else to do because they were on our side,' she tweeted.

Davidsen was then careful to note: 'I am also 100% positive that Facebook activity recruits and staffs people that are on the other side.'

Davidsen posted this in the wake of the uproar over Cambridge Analytica, and their mining of information for the Trump campaign.

Hillary Clinton meanwhile refused to access the API that had been created by the Obama campaign with this Facebook information.

'I worked on all of the data integration projects at [Obama for America]. This was the only one that felt creepy, even though we played by the rules, and didn't do anything I felt was ugly, with the data,' stated Davidsen.

The revelations, if true, mean that Obama's campaign used similar tactics to those of Cambridge Analytica, which worked on President Donald Trump's election campaign, and reportedly harvested private information from more than 50 million Facebook users.

Members of Congress called on Facebook CEO Mark Zuckerberg to testify about Facebook's actions on Monday in the wake of the revelation.

Meanwhile, British privacy regulators are seeking a warrant to search the offices of the U.K.-based Cambridge Analytica as both US and European lawmakers demand an explanation of how the consulting firm gained access to the data.

The news also saw Facebook shares closed down nearly 7.0 percent on Monday, wiping nearly $40 billion off its market value as investors worried that new legislation could damage the company's advertising business.

Members of Congress called on Facebook CEO Mark Zuckerberg to testify about Facebook's actions on Monday in the wake of the revelations about Cambridge Analytica

Facebook said on Monday it had hired forensic auditors from the firm Stroz Friedberg to investigate and determine whether Cambridge Analytical still had the data.

'Auditors from Strop Fried berg were on site at Cambridge Analytic's London office this evening,' the company said in a statement late Monday. 'At the request of the UK Information Commissioner´s Office, which has announced it is pursuing a warrant to conduct its own on-site investigation, the Strop Fried berg auditors stood down.'

Yet the Obama campaign may have harvested information from millions during the 2012 run.

Of course, the biggest difference is that those signing up to the Obama campaign did so knowingly. While with Cambridge Analytic, users were told they were contributing to an academic research project. That information was then passed to the Trump campaign.

But that doesn't mean the friends of the Obama supporters consented to have their details used in their data mining.

The New York Times Magazine reported how the campaign had a list of a million people who had signed into the campaign website through Facebook.

This information obtained by Cambridge Analytica is said to have been used to help elect President Donald Trump in the US, as well as to boost the Brexit campaign in the UK. CEO Alexander Nix has said the firm was 'always acquiring more' data

To do so, they were prompted to agree to grant the campaign permission to access their Facebook friends list, photos and other personal information.

Another prompt, which most people also agreed to, asked for them to grant access to their news feed.

Through these prompts, the campaign had access to millions of people, and their interests, and friends - who they could note down as potential donors, unregistered voters and persuadable votes - to target in specific campaigns.

One staffer said that once a supporter signed up through Facebook, it would take them mere seconds to go through their friends' lists, match them with votes lists, and then they would go through photos - trying to weed out old girlfriends and college friends who could share their political beliefs.

The campaign reportedly mined data from 15 million Facebook users, which triggered alarms at the social media giant, but the company always decided that the campaign had not violated its privacy and data rules.

Facebook did not respond to reporters' requests for comment.