The decision by the High Court of Australia, sitting in Canberra, in effect allows litigants to mount libel cases anywhere in the world over website material, not just in the website’s country of origin.

International media organisations that have a strong internet presence are deeply concerned. They fear that anybody who objects to a website article, particularly celebrities or politicians, will be tempted to sue in a country that has favourable defamation laws.

The ruling, that internet content is deemed to have been published in any place where it is viewed online, means that a website publisher could face multiple defamation actions from countries with the strictest libel laws, such as Britain.

In a unanimous judgment, the Canberra High Court dismissed an appeal by the international news agency Dow Jones to have a defamation action, brought by the Melbourne businessman Joseph Gutnick, heard in the United States. Instead the court ruled that the case could be heard in his home state of Victoria.

Mr Gutnick, a mining magnate, had sued the American-based news agency over an article that appeared on Barron’s website, which is published by the owners of The Wall Street Journal and Dow Jones.

Mr Gutnick argued that the proceedings should take place in Melbourne, where the article was downloaded. Dow Jones wanted the case to be heard in America, where the story was written and posted on the internet.

In America publishers enjoy freedom-of-speech protection under the First Amendment, unlike some other countries where more draconian defamation laws are heavily weighted in favour of the claimant. Australia has some of the strongest libel laws in the world.

Mark Stephens, a lawyer for Dow Jones, said: “This is a very worrying decision. Are those who provide material on the internet, such as newspapers, going to have to filter their stories with a view to the country which might receive them? “Under this ruling, would we see The Times dragged before the courts of Indonesia for its coverage of bombing atrocities if someone there thought this libellous?” One of the judges, Mr Justice Kirby, had urged reform to tackle the problem, Mr Stephens said. “One proposal floated at the recent International Bar Association conference is that people could sue anywhere but the article would be judged by the laws of the country where it was published.”

Mr Stephens added that libel lawyers in Britain could see a boom in business as here the burden of proof is on the defendant. “People will look around and bring libel actions in countries that are nothing to do with the article concerned.”

Mr Gutnick welcomed the decision because it would “re-establish that the net is no different than the regular newspaper”.

He added: “You have to be careful what you write and if you offend somebody or write malicious statements about people you can be subject to being prosecuted.”

The Internet Industry Association said that it would be “another straw in the camel’s saddle bag” for online publishers. Many might be tempted to give up, he said.