Internet sites could be fined or blocked if they fail to tackle "online harms" such as terrorist propaganda and child abuse, under government plans.
The Department for Digital, Culture, Media and Sport (DCMS) has proposed an independent watchdog that will write a "code of practice" for tech companies. Senior managers could be held liable for breaches, with a possible levy on the industry to fund the regulator. But critics say the plans threaten freedom of speech.
The Online Harms White Paper is a joint proposal from the DCMS and the Home Office. A public consultation on the plans will run for 12 weeks.
The paper suggests:
l establishing an independent regulator that can write a "code of practice" for social networks and internet companies
l giving the regulator enforcement powers including the ability to fine companies that break the rules
l considering additional enforcement powers such as the ability to fine company executives and force internet service providers to block sites that break the rules Outlining the proposals, Culture Secretary Jeremy Wright said: "The era of self-regulation for online companies is over. Voluntary actions from industry to tackle online harms have not been applied consistently or gone far enough."
Discussing potential penalties on BBC Breakfast, he said: "If you look at the fines available to the Information Commissioner around the GDPR rules, that could be up to 4% of company's turnover... we think we should be looking at something comparable here."
The plans call for an independent regulator to hold internet companies to account. It would be funded by the tech industry. The government has not decided whether a new body will be established, or an existing one handed new powers.
The regulator will define a "code of best practice" that social networks and internet companies must adhere to.
As well as Facebook, Twitter and Google, the rules would apply to messaging services such as Snapchat and cloud storage services. The regulator will have the power to fine companies and publish notices naming and shaming those that break the rules.
The government says it is also considering fines for individual company executives and making search engines remove links to offending websites.
It is also consulting over blocking harmful websites.
And freedom of speech campaigners Article 19 warned that the government "must not create an environment that encourages the censorship of legitimate expression".
A spokesman said it opposed any duty of care being imposed on internet platforms.
They said that would "inevitably require them to proactively monitor their networks and take a restrictive approach to content removal".
"Such actions could violate individuals' rights to freedom of expression and privacy," they added.
