STOCKHOLM (Reuters) - A copyright test case involving one of the world’s biggest free file-sharing websites that could help music and film companies recoup millions of dollars in lost revenues started on Monday in Stockholm.

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Four men linked to The Pirate Bay were charged early last year by a Swedish prosecutor with conspiracy to break copyright law and related offences.

Companies including Warner Bros., MGM, Columbia Pictures, 20th Century Fox Films, Sony BMG, Universal and EMI are also asking for damages of more than 100 million crowns ($12 million) to cover lost revenues.

Sites like The Pirate Bay allow people to download songs, movies and computer games without paying and the trial is being closely watched to see to what extent the entertainment industry can protect copyright against Internet users.

“This is not a political trial, it’s not about shutting down a people’s library and it’s not a trial that wants to prohibit file sharing as a technique,” said Monique Wadsted, a lawyer representing Warner Brothers, Columbia, MGM and other major media and computer games companies.

“It’s a trial regarding four individuals that have conducted a big commercial business making money out of others file sharing ... copyright protected works.”

The accused -- Peter Sunde, Gottfrid Svartholm Warg, Fredrik Neij and Carl Lundstrom -- denied the charges.

The group that controls The Pirate Bay, launched in 2003, says that since no copyrighted material is stored on its servers and no exchange of files actually takes place there, they cannot be held responsible for what material is being exchanged.

The prosecution says that by financing, programing and administering the site, the four men promoted the infringement of property rights by the site’s users.

The trial could last as long as three weeks and the four accused face up to two years in jail if convicted.