Facebook shares took a hit overnight plummeting to US$30bn after news broke that controversial political research company Cambridge Analytica retained information of 50 million users without permission.

Yesterday its shares opened at US$177.01 and dropping to US$170.06. Currently its stocks sit at US$172.56, down 6.7 per cent.

Bloomberg reports this has been its biggest drop since 2015.

Cambridge Analytica has links to US President Donald Trump and his 2016 campaign.

Lawmakers in both the UK and US are reviewing Facebook and its role in both Brexit and the 2016 US election. Politicians from both countries are demanding CEO Mark Zuckerberg to appear before them to explain how Cambridge Analytica was able to obtain all this data which in turn helped Trump win the election.

Facebook has suspended Cambridge Analytica and two associated individuals after receiving reports they violated the company’s third-party developer terms on the collection of user data.

On Saturday, Facebook said one of the individuals, Aleksandr Kogan shared user data from his personality quiz, ‘thisisyourdigitallife’ to Cambridge Analytica. Facebook says this is not an official data breach as he collected the data through legitimate means.