The chilling effect of libel laws on free speech has become "dangerous and intolerable," campaigners warned at a fringe event at the Liberal Democrat party conference.
Speaking to a packed audience on Sunday, journalists and representatives of Sense About Science said that British libel law must be reformed to protect scientific debate.
Science writer Simon Singh spoke of his own experience fighting a libel case against the British Chiropractors' Association, which sued him over an article criticising claims that chiropractics can cure asthma.
The cost of defending such cases is prohibitively high.
"We have a libel system where victory means still losing £50,000 and two years of your life - never mind what losing means," Singh said.
Worse still, he added, the risk of libel actions leads many journalists not to publish in the first place.
"Libel isn't just about those cases that go to court - it's about all the other articles that never get printed."
Ben Goldacre, author of Bad Science, went further, saying that British libel law had become a "serious public health problem".
Open scrutiny of medical claims was essential to ensure scientific progress and protect public safety but fear of libel actions stifles the debate.
Goldacre has successfully defended himself from a libel action by a salesman advertising vitamin pills as a cure for AIDS.
Journalist Nick Cohen said that Britain's influence elsewhere in the world and the prevalence of 'libel tourism' meant our libel laws were "becoming a global threat to freedom of speech".
Evan Harris, MP for Oxford and Lib Dem spokesperson on science, agreed, saying London had become "the libel capital of the world".
Some audience members questioned whether loosening libel laws might lead to poorer quality journalism.
But the panellists rejected this argument, saying the strictures of libel law were damaging journalism, not reigning in its excesses.
They insisted that relaxing libel laws did not mean 'open house' on slander.
Malicious claims - those showing wanton disregard for the truth - would still be covered.
Hours after the event, conference passed an amendment calling for the reform of libel laws to protect free speech.
Professor Richard Dawkins, although not a member of the Liberal Democrats, spoke in favour of the motion after being granted special permission to attend.
