Increasing legal action in the United States over piracy on YouTube, the video-sharing website, could set the scene for a test case against a British bootlegger, lawyers said.

In the latest move, Twentieth Century Fox has demanded that YouTube reveal details of an American user who posted episodes of 24 and The Simpsons on the site.

With analysts suggesting that relationships between YouTube and content owners could be deteriorating over piracy problems, lawyers are warning parents to be cautious about their children uploading bootlegged material.

Struan Robertson, a senior associate with Pinsent Masons and the editor of out-law.com, the technology law website, said: “Many seem to be under the impression that using, for example, a pop song as the backing track to an amateur video is lawful. It is not.”

He added: “We are likely to see action against an individual in the UK — a test case which will send out a message that it is not OK to use copyrighted material on the web. We have seen in it the music industry; it is not hard to predict it will happen in the TV industry.”

The move by Twentieth Century Fox, the television group owned by News Corporation, parent company of The Times, underlined the tensions between content owners and so-called Web 2.0 sites, which depend on users uploading content to drive advertising revenues. YouTube, bought by Google last year for $1.65 billion, records more than 100 million video downloads a day.

Film studios, television companies and music labels, many of which now have commercial deals in place with YouTube, still argue that such volumes would be impossible if it were not for pirated material.

Google has in the past been protective of its users’ identities and YouTube removes copyrighted material once alerted. However, facing legal action, YouTube said that it will hand over evidence. The site has already supplied details of at least one user to Paramount, the film studio. Last night, a YouTube spokesman said: “We received a subpoena [from Fox] and will comply with valid US legal process.”

Content owners are growing increasingly frustrated with the existing arrangement, in which they are called on constantly to monitor video-sharing sites. According to the terms of the European directive that governs copyright law in the UK, YouTube is not obliged to police its users proactively.

YouTube, already targeted with several lawsuits from record labels, has sought to pacify content owners by developing a system that will automatically filter out copyrighted material. However, the technology is running late and content owners are lobbying hard in Brussels for a change in the law.

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