The Pirate Bay is facing a ban in the UK following a ruling by the High Court.
Judge Richard Arnold declared that the website encourages users to infringe on music copyright, paving the way for broadband providers to block the service.
Pirate Bay provides a searchable index of links to BitTorrent trackers, primarily films, music and software. It claims to be the largest website of its kind, with 3.7 million hits in the UK alone.
Record labels and film studios have long opposed the service, and attempted legal action on numerous occasions. The Pirate Bay's defenders claim that it is no more illegal than Google, but Mr Justice Arnold ruled that it encourages illegitimate practices.
"In my judgment, the operators of [The Pirate Bay] do authorise its users' infringing acts of copying and communication to the public," he said. "They go far beyond merely enabling or assisting," adding that its users have "a common design to infringe".
"I conclude that both users and the operators of [The Pirate Bay] infringe the copyrights of the Claimants (and those they represent) in the UK."
Pirate Bay, which moved away from torrent hosting last week, was not represented in the UK court. The site's organisers were hit by criminal convictions in 2009 in their native Sweden.
"Despite their ability to do so and despite the judicial findings that have been made against them, the operators of [The Pirate Bay] take no steps to prevent infringement," Arnold added.
"On the contrary, as already explained, they actively encourage it and treat any attempts to prevent it (judicial or otherwise) with contempt."
Long-time Pirate Bay opponent the British Phonographic Industry (BPI) praised the court's decision, and vowed to continue to put pressure on service providers to take action against the website.
"The High Court today ruled that The Pirate Bay is illegal. The site defrauds musicians and causes huge damage to the music industry and wider creative industries," said BPI chief executive Geoff Taylor.
"The ruling helps clarify the law on website blocking and we will now proceed with our application to have the site blocked to protect the UK's creative industries from further harm."
The move follows Hollywood's landmark victory over torrent website Newzbin2, which saw the service blocked by BT and Sky. The case was expected to set a legal precedent for copyright holders to tackle other websites deemed guilty of infringement.