The Democrats petition singled out top two officials of Department of Special Investigation, director general Tarit Pengdith and his deputy Pravesana Mulpramook, for lapse of duty in their enforcement of the lese majeste law.
Suthep said he wanted the NACC to probe the two officials on two separate cases.
In the first case, Tarit had made several comments in the press about the existence of a conspiracy to topple the monarchy. But after a change of government, he abruptly submitted the DSI report to the public prosecutors recommending for charges be dropped.
Suthep said he suspected Tarit and Pravesana had drawn an unlawful conclusion because the two did not make reasonable efforts to collect evidence.
In the second case, Tarit spearheaded the DSI investigation on royal insult involving red-shirt leader Jatuporn Promphan in connection to his rally speech in April 2011. The investigative work had progressed to the point that the Criminal Court agreed to revoke the bail for Jatuporn last May.
The bail was previously granted to Jatuporn on terrorism charges in connection with the 2010 political mayhem.
Due to suspicion of his alleged royal insult, the DSI managed to put him in the remand cell until his release last August following the general election in which he won a House seat.
Suthep said Tarit made an about-turn on May 10 to drop royal insult charges against Jatuporn. He added that the DSI chief appeared to have made two conflicting conclusions on the Jatuporn case, one of which was definitely wrongful because an individual suspect could not be guilty and not guilty in the same case.