In a major report, MPs also warned democracy was at risk from the “malicious and relentless” targeting of citizens with disinformation and adverts from unidentifiable sources as they called for reform to electoral communication laws.
The digital, culture, media and sport committee singled out Facebook for criticism, accusing the platform of being “unwilling to be accountable to regulators”.
Committee members rounded on Facebook chief Mark Zuckerberg, who was accused of showing “contempt” by choosing not to appear before the body last year.
The report said: “Companies like Facebook should not be allowed to behave like ‘digital gangsters’ in the online world, considering themselves to be ahead of and beyond the law.”
The report also said ethics guidelines were needed to set out what was and was not acceptable on social media, including harmful and illegal content that has been referred to the platforms by users or identified by the companies.
If tech firms fail to meet their obligations under the code, then an independent regulator should be able to launch legal proceedings against them and have the power to issue large fines, the MPs said.
They wrote: “Social media companies cannot hide behind the claim of being merely a ‘platform’ and maintain that they have no responsibility themselves in regulating the content of their sites.”
In response, Facebook’s UK public policy manager Karim Palant said: “We share the committee’s concerns about false news and election integrity and are pleased to have made a significant contribution to their investigation over the past 18 months, answering more than 700 questions and with four of our most senior executives giving evidence.
“We are open to meaningful regulation and support the committee’s recommendation for electoral law reform, but we’re not waiting. We have already made substantial changes so that every political ad on Facebook has to be authorised, state who is paying for it and then is stored in a searchable archive for seven years. No other channel for political advertising is as transparent and offers the tools that we do.
“We also support effective privacy legislation that holds companies to high standards in their use of data and transparency for users. While we still have more to do, we are not the same company we were a year ago. We have tripled the size of the team working to detect and protect users from bad content to 30,000 people and invested heavily in machine learning… to help prevent this type of abuse.”
In the past year Facebook has come under intense pressure over some of its business practices, following the Cambridge Analytica scandal, a series of data breaches and concerns over fake news and other content on the site.
The committee’s final report into disinformation and fake news said electoral law was “not fit for purpose” and should be updated to reflect the move to “microtargeted” online political campaigning.
They called for a comprehensive review of the rules and regulations surrounding political work during elections and referenda.
Ministers were also asked to reveal how many investigations were being carried out into Russian interference in UK politics.