Nice to see that his ongoing legal battle has not prevented science broadcaster Simon Singh from doing what he does best - electrocuting gherkins. At least this is what he did on 29 June at London's Bloomsbury Theatre to demonstrate that all elements have a unique colour (gherkins glow orange when fired up because of the sodium in the preserving salt), which was his typically pithy and fun way to explain the "red shift" effect that allows scientists to hypothesise that the Universe is expanding. Simon's performance was the finale to the latest benefit gig for the Rationalist Association, Night of Four Hundred Billion Stars (And Maybe Some String Theory), devised and organised, like last year's Godless Christmas shows, by comedian Robin Ince.

Simon Singh spoke only about cosmology, but there were few in the audience who were not also aware that he is currently embroiled in a very important libel case with the British Chiropractic Association over a 2008 Guardian article in which he accused them of promoting "bogus" treatments. Singh says by "bogus" he meant that there was no scientific foundation for the claims that chiropractic works for a range of conditions including colic and asthma. But the judge in the case, the somewhat notorious Mr Justice Eady, ruled against Singh in May. Eady's judgement hinged on the meaning of "bogus", which, he said, implied that the BCA had deliberately promoted false treatments. A second aspect of his ruling was to say that, although the piece appeared on the comment pages of the Guardian, what Singh says was presented as "fact" (comment is protected in libel law). So now Singh faced costs of at least £100,000 and a dilemma.

Although it is risky to appeal (he could personally incur costs up to £500,000) and the chances of an appeals court overturning a "meaning" ruling from another judge are slim, Singh has vowed to fight on. Despite the risks he thinks there is a chance that the appeals court might rule in his favour, and he feels that the case is of such importance that he should continue. For while he would really like a chance to argue the scientific evidence with the BCA in court, the "meaning" ruling now makes that aspect irrelevant, and the fight has implications far beyond assessing chiropractic.

This is why a huge wave of support has gathered round Singh - online, at a packed public meeting in May, and now in the campaign organised by the pressure group Sense About Science called Keep Libel Laws Out of Science. The basic case is that there is nothing wrong with having laws protecting people from being defamed, but the prohibitive cost of libel actions (for which no legal aid is available) favours those with huge resources, and discourages journalists and publishers from saying things that powerful organisations or individuals might find inconvenient. This is especially worrying for science, where rigorous public research is vital to provide a counterweight to the interests of multi-million-pound companies. While Singh, as he admits, is fortunate enough to have the resources to fight on, this would not be case for most journalists, nor even for many newspapers or publishers, who are far more likely to withdraw than stand up and fight because of the huge financial risks.

The campaign seems to be gathering momentum. We have learned that meetings are taking place between the science campaign and those - like PEN and Index on Censorship - who have long been campaigning for libel reform because of the way it impinges on free speech. This is also a campaign that has the chance to cut across political lines. Last year the right-wing Centre for Social Cohesion organised a conference that highlighted "libel tourism" - the practice by which foreign nationals are using British courts (where libel penalties are something like 140 times the European average) to suppress the publication of material, sometimes written by non-Brits and published outside Britain. One of Singh's proposals is for a kind of small claims court for libel, which would reach judgements within a month and ensure proportionality in terms of costs. This would prevent the situation he is now in, where the BCA are claiming only nominal damages, but he stands to lose half a million.

If the campaign can grab the moment, it has the chance to force comprehensive reform of libel laws. Then maybe Simon Singh can get back to the important work of zapping preserved vegetables.

Correction: This article has been changed from the print version (New Humanist, July/August). In the original we referred to "claims that chiropractic works for a range of conditions including colic and hyperactivity". Simon Singh has pointed out that he did not refer to "hyperactivity" in his Guardian article, but he did refer to "asthma". We have amended this accordingly.