Michael Silverleaf QC told a case management conference at the high court in London on Friday that "we are dealing with 500 claims, potentially" from people who say their voicemail messages were intercepted by the now-defunct News of the World.
Murdoch's News Group Newspapers has paid millions of pounds to settle lawsuits from 60 actors, athletes, politicians and other public figures whose voicemails were hacked by the tabloid.
More than 45 new cases are due to go to court, with claimants including soccer star Wayne Rooney and Cherie Blair, wife of former Prime Minister Tony Blair.
Murdoch closed the News of the World last July amid an outcry over its wrongdoing.
