"How can he (Najib) assume that all those who did not attend the congress did not receive the notice?" he asked.
The daily had quoted Najib as saying that DAP had no credibility as it did not practise democratic principles within its own party.
The ROS came into the picture after complaints of electoral fraud surfaced in the aftermath of the party's central executive committee elections last December.
Party secretary-general Lim Guan Eng's political secretary Zairil Khir Johari had initially received 305 votes but, after what was claimed to be a technical error, was subsequently pronounced as having 803 votes.
Subsequently, the ROS issued DAP with a directive to hold fresh elections.
Last Thursday, DAP said it would comply with the directive to avoid possible de-registration of the party.