The suit, filed in June by Mohamad Saiful Bukhari Azlan, seeks damages of 50 million ringgit ($15.7 million) and adds to mounting headaches for the opposition leader.
Anwar, 67, is fighting to overturn a March criminal conviction on charges that he sodomised Saiful in 2008, a ruling that Anwar calls a smear by the ruling United Malays National Organisation (UMNO).
Anwar is currently also embroiled in a bitter dispute with a member of his three-party opposition alliance that threatens to break apart the coalition, whose recent electoral successes have put severe pressure on UMNO's long-ruling regime.
Anwar's lawyers said he must file a defence to Saiful's civil suit on September 3.
"It is politically motivated to smear Anwar's name. It is a baseless suit which we will defend vigorously in court," said N. Surendran, Anwar's counsel.
AFP