Tory former cabinet minister David Davis is to spearhead a campaign against the Government’s new internet legislation, branding it a “censor’s charter”.

Mr Davis compared the Online Safety Bill to George Orwell’s dystopian novel, 1984, accusing ministers of outsourcing the policing of the internet to the big tech companies.

He backed a report by the Index On Censorship campaign group which warned that while free speech for journalists and politicians would be protected, many ordinary people could have perfectly legal posts banned.

When the Bill was published in May, the Government said it was intended to ensure material such as images of child sex abuse, terrorist material or content inciting racism or violence, was taken down.

However the report said the “duty of care” model it proposed – based on health and safety legislation – was “overly simplistic”.

The Bill would force the tech companies to delete posts which are considered “harmful” – with heavy fines of up to 10% of turnover if they fail to do so – in a system overseen by Ofcom.

But the report said the Government’s failure to define what constitutes “harmful” material in the Bill would result in many perfectly legal posts banned.

It said the threat of huge fines was “highly problematic” and could lead to “over-censorship” by the Silicon Valley giants who failed to appreciate “irony loving Brits”.

While it welcomed the aims of the legislation, it said it would actually make it harder for law enforcement to tackle abusers as it would require the tech companies to delete material before it could be reported to the police.

Mr Davis said: “The Online Safety Bill is a censor’s charter. Lobby groups will be able to push social networks to take down content they view as not politically correct, even though the content is legal.

“The idea we should force Silicon Valley companies to police Briton’s speech online seems out of Orwell’s 1984 and is not what our voters expect of us.”

Index On Censorship chief executive Ruth Smeeth said it would be “catastrophic” for freedom of speech.

“We work with people across the globe who are being censored by oppressive regimes. It might not be the UK Government’s intention but this Bill sets a worrying international precedent. Dictators around the world will be taking notes,” she said.

Gavin Millar QC, who is also backing the campaign, said it was “inevitable” that the legislation would be challenged in the courts.

“The scale of the task given to platforms, and the vagueness of wording in the legislation will force broad ‘technical’ solutions to content moderation – such as overly restrictive algorithms which will make decisions without context, nuance and an understanding of our laws and culture,” he said.

“This could lead to large quantities of content being blocked wrongly. Judgments that should be reserved for UK prosecutors and the courts will be outsourced to global tech companies.”