Laws aimed at regulating the newspaper industry will pose "the most substantial threat to British press freedom in the modern era", campaigners have warned.
A report by freedom of speech experts claims recommendations made following the Leveson inquiry into practices and ethics within the industry will have a serious and long-term impact on the media and democracy.
The document, Leveson's Illiberal Legacy, says a state-backed regulator underpinned by a Royal Charter would pose "imminent danger" to local newspapers, and would have made it "impossible" for the MPs' expenses scandal to have surfaced.
It calls on the Government to repeal sections of the Crime and Courts Act and to annul the Royal Charter.
The report, backed by the Free Speech Network and advised by some of the key freedom of expression campaigners behind the Libel Reform Campaign, claims it is a "myth that Leveson protects human rights".
Professor Tim Luckhurst, who wrote the report's foreword, said: "The impact of state-sanctioned regulation on our precious local newspapers would be uniquely harsh and spectacularly unjust.
"They serve their communities brilliantly. Surely they deserve our protection: their demise would impoverish local communities and cripple local democracy."
Report author Helen Anthony said: "From November, newspapers not signed up to a state recognised regulator could be hit with exemplary damages in libel and privacy proceedings.
"Shortly afterwards, punitive costs awards could be made against newspapers sued for similar proceedings, even if they have broken no laws. This is deeply unfair and prevents free speech. This is bad law, and it was made in a rushed, undemocratic manner."
Responding to the report, Dr Evan Harris of the Hacked Off campaign group in favour of media regulation, said: "Its desperate rhetoric - comparing the Leveson system to that of repressive regimes - and claiming that an independent self-regulator amounts to the end of press freedom - betrays a recognition by the press executives behind the report that the public will never accept the rejection of the Leveson Inquiry, and calls instead for politicians 'to come to heel' and reject the Leveson Report, repeal the incentives and annul the Royal Charter.
"The document fails to provide any proper evidence that acceptance of the Leveson system by the press would have any impact on public interest journalism (like the MPs expenses story), and avoids mentioning that all these publishers have already signed up to a system in Ireland which has similar ingredients to Leveson but which lacks the political independence that Leveson and Royal Charter enshrine."