Google, Facebook and Twitter should be held liable for illegal and dangerous content on their platforms, an ethics body has said.
Prime Minister Theresa May has said companies need to remove extremist content quickly or face fines.
One free speech advocate said it could turn Facebook into a "national censor".
Lord Bew, who chairs the CSPL, told the Times he was normally "allergic" to proposing new legislation but the decision came out of frustration with how the big technology companies were currently addressing the issue.
The suggested legislation forms part of a report into intimidation in public life, due to be published on Wednesday, 13 December.
An earlier parliamentary inquiry, published by the Commons Home Affairs Committee in May, concluded that technology companies were "shamefully far" from taking action to tackle illegal and dangerous content.
In response to the news, Jim Killock, executive director of the Open Rights Group, said: "This is an attempt to make [Facebook boss] Mark Zuckerberg a national censor.
"Facebook and Twitter will censor legal material because they are scared of fines.
"They are the worst people to judge right and wrong."
In response to the suggested legislation, Twitter said: "Abuse and harassment have no place on Twitter.
"We're now taking action on 10 times the number of abusive accounts every day compared to the same time last year.
"We also now use technology to limit account functionality or place suspensions on thousands more abusive accounts each day."