Campaigners have labelled the Online Safety Bill “flawed” and “disastrous” for privacy and free speech following the draft publication of the new internet safety rules.

The Bill will require firms to abide by a duty of care to their users, with regulator Ofcom able to levy large fines and even block access to sites that do not comply.

The largest platforms will also be expected to clamp down on content that is considered “legal but harmful”, including posts linked to topics such as self-harm or those that contain disinformation.

But campaign groups have suggested that this approach is too vague and could lead to free speech being eroded.

Mark Johnson, legal and policy officer at civil liberties and online privacy group Big Brother Watch, said: “The Online Safety Bill introduces state-backed censorship and monitoring on a scale never seen before in a liberal democracy.

“This Bill is disastrous for privacy rights and free expression online. The Government is clamping down on vague categories of lawful speech. This could easily result in the silencing of marginalised voices and unpopular views.

“Parliament should remove lawful content from the scope of this Bill altogether and refocus on real policing rather than speech-policing.”

Jim Killock, executive director of the digital rights organisation Open Rights Group, said that the Government’s approach of “treating online speech as inherently dangerous” and “demanding that risks are eliminated under the threat of massive fines” would only lead to “over-reaction and content removal”.

The idea that private messages should be routinely checked and examined is extraordinary.

Mr Killock said the Bill’s approach was insufficient because it pushes the platforms to monitor themselves rather than regulate them fully and independently.

“This is a flawed approach which makes no attempt to bring lawbreakers to justice,” he said.

“Instead, it tries to put the problem solely on the shoulders of platforms. But Facebook is not the police and does not operate prisons.

“It also pushes for lawful content, including in-private messages sent through these platforms, to be monitored and scoured for alleged risks. The idea that private messages should be routinely checked and examined is extraordinary.

“This is a litmus test for the Conservative Party and the Prime Minister over how committed they are to the principles of free speech.”

The Government has defended its approach, with Digital Secretary, Oliver Dowden, calling the proposed laws “ground-breaking” and the means to “usher in a new age of accountability for tech and bring fairness and accountability to the online world”.