From CNBC:

Britain's Online Safety Bill would make it mandatory for social media services to tackle both illegal posts as well as material that is "legal but harmful," a vague definition that has attracted criticism from some in the tech industry over concerns that it may stifle free speech.

"Twitter and all social media platforms must protect their users from harm on their sites," a U.K. government spokesperson told CNBC.

"We are introducing new online safety laws to safeguard children, prevent abusive behaviour and protect free speech," the spokesperson said. "All tech firms with users in the U.K. will need to comply with the new laws or face hefty fines and having their sites blocked."

The stakes for platforms like Twitter would be even higher under the Online Safety Bill, which threatens jail time for company executives for serious violations, as well as penalties of up to 10% of annual global sales.

The legislation, which is yet to be approved by U.K. lawmakers, is expected to become law later this year.

Musk said earlier in the day after the EU's threats were issued that, "The extreme antibody reaction from those who fear free speech says it all."

"By 'free speech', I simply mean that which matches the law. I am against censorship that goes far beyond the law. If people want less free speech, they will ask government to pass laws to that effect. Therefore, going beyond the law is contrary to the will of the people," Musk said.