The Libel Reform Campaign is calling on supporters to make a "final push for a truly fair and effective Defamation Bill", as it prepares for a lobby in parliament on Wednesday (27th June).
Comedian Dara Ó Briain, physicist Brian Cox and writer Dave Gorman will be among supporters of the campaign, organised by charities Index on Censorship, English PEN and Sense about Science.
The Defamation Bill, introduced in the Queen's Speech in March, promises long-awaited reform on libel law, with measures to reduce libel tourism and end the multiple publication rule, both issues which affect book publishers.
However the Libel Reform Campaign says the Bill has "failed to put forward a usable public interest defence and offers no restrictions on the ability of corporations to silence critics."
The campaigners warn: "Unless these issues are addressed there remains the possibility that the threat of libel action will still be used to bully newspaper journalists, scientists, bloggers, consumer groups, human rights activists and others."
The campaign is urging supporters to write to their MP calling for the necessary changes to be made to the Bill, and to join the lobby on Wednesday.