U.S. based Facebook and Twitter and China-owned TikTok could be fined up to 10% of turnover, according to Reuters. CNBC reported that Ofcom, a British media watchdog, would have the power to enforce the laws if they are enacted.

Under the proposal, which will be introduced next year, social media companies must establish clear terms and conditions about content, CNBC reported.

"We are entering a new age of accountability for tech to protect children and vulnerable users, to restore trust in this industry and to enshrine in law safeguards for free speech," Britain's Digital Secretary Oliver Dowden said Tuesday.

In addition to fines, some sites could be blocked from the British market if they fail to act.

Dowden left open the possibility for criminal charges against companies that permit illegal content, according to Reuters.

"These measures make this the toughest and most comprehensive online safety regime, and they will have a clear and immediate effect," he told lawmakers.

But the proposals don’t stop at illegal content. According to Reuters, the proposed legislation would require companies to have clear policies against misinformation that could cause “harm,” such as information about COVID-19 vaccines.

"We already have strict policies against harmful content on our platforms, but regulations are needed so that private companies aren't making so many important decisions alone," said Rebecca Stimson, Facebook’s head of Britain public policy.

Other Big Tech companies echoed Facebook.

Under the proposed laws, online journalism and user comments on news sites would be exempt to "safeguard freedom of expression," Reuters reported.

Britain’s move comes as the European Union was also set to unveil a slate of similar proposals on December 15.