Papua New Guinea's Police Commissioner Tom Kulunga says opposition leader Belden Namah has filed an official complaint against Prime Minister Peter O'Neill for his alleged involvement in the fraudulent payment to Paul Paraka lawyers.
Mr Paraka was arrested last month and charged with 18 fraud offences, related to payments from Government departments to the order of 25 million US dollars.
Two other lawyers were also arrested.
Commissioner Kulunga says he has written to Mr Namah saying the complaint is already being investigated by the Task Force Sweep Team.
He also added the investigations are at an advanced stage and people have been interviewed.
Police Commissioner Kulunga says Mr Namah's documents have already been made available to the Chairman of the Task Force Sweep Team, and it would be counter-productive to institute another investigation.
He says Peter O'Neill is also the acting Minister for Police and it is in the best interest of all parties concerned that the matter is handled by the Task Force Sweep Team to avoid any suggestion of bias.