For the past 20 years I have been a science journalist, working on programmes such as Horizon, writing popular science books, publishing articles in national newspapers and occasionally presenting programmes about physics or mathematics. About 12 months ago, however, my career all but ground to a halt when I received a letter accusing me of libel. Today I am still fighting that libel action, but more importantly I am campaigning for reform of the English libel laws and hoping that everyone who cares about the free discussion of ideas will join me.

My current predicament has its origins in a book I co-authored with Edzard Ernst, the world's first professor of complementary medicine. Trick or Treatment? looked at the evidence for and against various alternative therapies. Although we showed that a few therapies were effective, the majority turned out to be unproven or disproven, and many seemed to be downright dangerous.

When the book was published in April 2008, I also wrote an article in The Guardian about the claims made by chiropractors to treat various childhood conditions. Could spinal manipulation really help children with asthma, colic and ear infections? Because of my legal situation, it is hard to go into detail, but the bottom line is that the British Chiropractic Association decided to sue me personally (not The Guardian) for libel.

Unfortunately, suing scientists and science writers seems to have become a fashionable sport. David Colquhoun, professor of pharmacology at University College London, was threatened with legal action last year over an article about chiropractors that he published in The New Zealand Medical Journal. The journalist Ben Goldacre, currently at Nuffield College, Oxford, was sued last year for criticising the promotion of vitamin pills to Aids patients in South Africa. And the British cardiologist Peter Wilmshurst is currently being sued for libel.

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I have no problem with someone suing me or suing anyone else for libel, because there should always be an opportunity for redress. However, my experience has shown me that the English libel system is deeply flawed - so much so that it has a damaging effect on journalism. There are numerous problems, but the key issue is the sheer cost of a libel case.

So far, I have accumulated bills of ?100,000, and someone who loses a libel trial could be ?1 million out of pocket. The majority of this money disappears in legal fees. Indeed, it is quite possible that 99 per cent of the money in a libel case will go to lawyers and only 1 per cent will go in damages to the claimant. There is no reason why our costs should be so extortionate and disproportionate to the damages involved; a recent report from the University of Oxford showed that fighting a libel action in England was 140 times more expensive than the European average.

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The impact of such extreme costs is that many journalists who are sued for libel will be forced to back down, apologise, settle early and pay compensation even if they are confident about the article under attack. Settling is often necessary because fighting on is in essence a no-win option. In my case, if I successfully defend my article, I will have had to have put my career on hold for probably two years, and it will cost me perhaps ?25,000 because I am unlikely to recover all my costs. And if I lose my case, then it will cost me roughly ?500,000. Fighting and winning is bad enough; fighting and losing is catastrophic.

So why am I fighting on? I stand by my article and do not want to apologise for something that I believe is accurate and important, particularly as it relates to childhood health. Also, I am in the very privileged position of being able to defend my article - because I have the time and the resources, and I have the support of family, friends, scientists, journalists and the public.

Moreover, my hope is that my particular case can highlight the problems in the English libel system and help encourage reform. Last week, I attended the launch of a campaign on this issue. The campaign already has support from cross-party MPs, and the timing is such that we are in a position to perhaps influence a Culture, Media and Sport Committee that is currently reviewing libel laws.

The Keep Libel Laws out of Science campaign released a statement arguing for reform of the libel laws. It has been signed by professors, journalists and famous names who care about science and free speech, including Stephen Fry, Ricky Gervais, Martin Amis, Carol Ann Duffy, Richard Dawkins and Lord Rees. If you also care about free speech and good journalism, please sign up to the statement.

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For more about the Keep Libel Laws out of Science campaign, visit