In his ruling last week that Assange should be extradited to Sweden, District Judge Howard Riddle accused attorney Bjorn Hurtig of deliberately misleading the court, calling him "unreliable."
Based on Riddle's comments, the bar association said it decided to demand Hurtig explain his actions, Swedish news agency Tidningarnas Telegrambyra reported Wednesday.
"We sent Hurtig a letter last week and asked him to explain himself," Bar Association Secretary-General Anne Ramberg said, calling Riddle's statements a "extremely serious critique" of the Swedish lawyer. "If I'm not satisfied with Hurtig's explanation, I may go to the bar association's governing board, and after that, the disciplinary committee, which has the final say on any possible consequences."
Riddle also said Hurtig, who testified at the extradition hearing, deliberately gave faulty information about how many times Swedish prosecutors tried to contact him concerning sexual assault allegations made against Assange in Sweden last summer.
Hurtig rejected the British judge's criticism, saying he was "a reliable person. I'm a reliable witness."
Hurtig has until March 14 to respond to the bar association's letter.