The Papua New Guinea opposition MP Belden Namah says Police Commissioner Gari Baki should resign.
The calls come after Mr Namah earlier this week said Prime Minister Peter O'Neill must step aside to allow a police investigation into his involvement in an alleged fraud involving a Port Moresby law firm.
Mr Baki had frustrated attempts by his own fraud squad to arrest Mr O'Neill.
He eventually disbanded the body.
It has since been allowed to continue its work but Mr Baki continues to be accused of interference.
Mr Namah said the Commissioner was under tremendous pressure from Mr O'Neill and should resign.
"If he is caught in a conflict of interest he has to step aside as well, and allow the anti-fraud and anti-corruption people to do their job."