The British Chiropractic Association dropped its libel action against the science writer Simon Singh today, filing a notice of discontinuation in the high court.

The case had become a cause celebre, with scientists, celebrities and freedom of speech campaigners lining up to condemn the British libel laws and argue that Singh had a right to express his opinion in print.

The sudden end to the case will strengthen the campaign for reform of the libel laws, which Jack Straw, the justice secretary, is considering. It is also a specific pledge in the Liberal Democrat manifesto.

Singh was sued by the BCA for a piece he wrote in the Guardian's comment pages, criticising the association for defending chiropractors who use treatments for which there is little evidence on children with conditions such as colic and asthma.

Singh and his supporters were dismayed by an early verdict by Mr Justice Eady on the meaning of the words used in the article. The judge ruled that Singh was stating facts, which he would have to prove in his defence, rather than voicing opinion and that he had implied the members of the BCA knowingly promoted what Singh called "bogus treatments".

Singh argued that was not what he meant and went to the court of appeal. Two weeks ago, he won the point.

In their ruling on the case, Lord Justice Judge, Lord Justice Neuberger and Lord Justice Sedley: "It is now nearly two years since the publication of the offending article. It seems unlikely that anyone would dare repeat the opinions expressed by Dr Singh for fear of a writ.

"Accordingly this litigation has almost certainly had a chilling effect on public debate which might otherwise have assisted potential patients to make informed choices about the possible use of chiropractic."

Robert Dougans of Bryan Cave LLP, who represented Singh, confirmed that the BCA's case was at an end. "All that now remains to be settled is how much of Simon's legal costs he can recover from the BCA, and how much he will have to bear himself," he said.

"However well this process goes, Simon is likely to be out of pocket by about £20,000. This – and two years of lost earnings, which he can never recover, is the price he has paid for writing an article criticising the BCA for making claims the Advertising Standards Authority has ruled can no longer be made. In the game of libel, even winning is costly and stressful.

"To have won this case for Simon is the proudest moment of my career, but if we had the libel laws we ought to have I would never have met Simon at all. Until we have a proper public interest defence scientists and writers are going to have to carry on making the unenviable choice of either shying away from hard-hitting debate, or paying through the nose for the privilege of defending it."

Ely Place Chambers, the chamber of William McCormick QC, one of two barristers who represented Dr Singh, said that the BCA had ended its "ill-fated" claim.

"Dr Singh's predicament as the sole defendant in an action brought in respect of a comment piece in the Guardian newspaper (to which the BCA never directed any complaint) was seen as a rallying point for those concerned about the abuse of UK libel laws in connection with scientific debate."