The left-wing candidate in Mexico's disputed 2 July presidential vote has filed a criminal complaint against the Federal Electoral Institute.
Lopez Obrador supporters are demanding a recount
Andres Manuel Lopez Obrador accuses the electoral authorities of letting business firms fund TV ads against him.
He has already filed a legal challenge, demanding a recount of the vote which saw him lose to conservative Felipe Calderon by half a percentage point.
The dispute has paralysed Mexican politics, correspondents say.
The case filed by Mr Lopez Obrador on Tuesday argues that the nine members of the electoral institute failed to stop private companies from funding ads which broke electoral regulations.
The pro-Calderon ads portrayed the leftist candidate as a danger to Mexico and compared him to Venezuelan President Hugo Chavez.
"They sowed fear in the citizens about the option that [Mr Lopez Obrador] represents," aide Horacio Duarte said.
He added: "It will be up to the public prosecutor to decide what crime might have been committed."
In a separate case, Mr Lopez Obrador will hear by the end of August whether a manual recount of votes will take place.
The leftist candidate says there is evidence that vote counts were rigged at about half of the country's polling stations - but European Union observers have said they found no irregularities.
Mr Calderon has rejected calls for a recount of the 41 million ballots cast, describing the election as "clean, free and democratic".
Mr Lopez Obrador's supporters have been staging mass protests to demand a recount.