While O'Neill said Namah conspired to overthrow his government and obtain warrants for his arrest, Namah has retaliated with claims of a cover-up and a "lack of impartiality" over police investigations.
Warrants to arrest O'Neill, Treasurer Don Polye and Finance Minister James Marape were issued in connection with a Task Force Sweep investigation into government payments of millions of dollars allegedly made to a law firm in Port Moresby.
It has since emerged that four police officers have been suspended for their involvement in issuing the arrest warrants but the opposition leader said there were no irregularities in the way the warrants were obtained.
Namah said both O'Neill and police commissioner Tom Kulunga had been misinforming the public.
"I'm of the firm belief that the actions of both the prime minister and the police commissioner in fact are moves to suppress any actions to eventually prosecute Prime Minister Peter O'Neill, Treasurer, core chairman of World Bank Don Polye and Finance Minister James Marape for very serious indictable offences," Namah told Radio New Zealand International.