Judge Tomas Norstrom denies he had a conflict of interest during the trial
Lawyers of four men convicted of running The Pirate Bay file-sharing website are seeking a retrial, saying the judge had a conflict of interest.
Judge Tomas Norstrom is a member of the Swedish Copyright Association and sits on the board of Swedish Association for the Protection of Industrial Property.
But the judge has told Swedish Radio: "These activities do not constitute a conflict of interest."
Sweden's Court of Appeal would rule on a possible retrial, the lawyers said.
Frederik Neij, Gottfrid Svartholm Warg, Carl Lundstrom and Peter Sunde were found guilty of breaking copyright law on 17 April 2009 and sentenced to a year in jail.
The four were also ordered to pay $4.5m (£3m) in damages to a number of entertainment companies, including Warner Bros, Sony Music Entertainment.
Peter Althin, who represents The Pirate Bay (TPB) spokesman Peter Sunde, said it was for the appeal courts to decide if there was to be a retrial, as it emerged the judge and lawyers for the entertainment industry were members of the copyright association.
"In the autumn I received information that a lay judge could have similar connections. I sent these to the court and the judge was excluded in order to prevent a conflict of interest. It would have been reasonable to then review this situation as well," Althin told Sveriges Radio.
Speaking to the BBC, Sven-Erik Alhem - a former senior attorney in Sweden - said the judge had made an error of judgement, but a retrial was unlikely.
"The judge should have told the parties of his other engagements. Had he done that then they could make a decision on whether they wanted him as a judge in their case.
Peter Sunde said he could not and would not pay his fine
"I'm not sure the superior court could say that this was unfair, but had he been open then it wouldn't have been an issue," he said.
Rick Falkvinge, leader of the Swedish Pirate Party, told the BBC the judge had made an "unforgiveable" decision.
"This is corruption and judicial decay at an unforgiveable level.
"The judge in one of Sweden's most high profile cases ever is also a member of an interest organisation for one side and associates with the prosecution trial lawyers in his free time? That is inexcusable corruption," said Mr Falkvinge.
The Pirate Bay file-sharing website was set up in 2003 by anti-copyright organisation Piratbyran, but for the past five years it has been run by individuals.
Millions of files are exchanged using the service every day.
No copyright content is hosted on The Pirate Bay's web servers. The site hosts BitTorrent links to TV, film and music files held on its users' computers.
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