In a television interview, Singson said the damages he is seeking are equivalent to Ilocos Surs share of the tobacco excise tax, of which P130 million was allegedly pocketed by Estrada as kickbacks.
Singson filed the libel suit with the prosecutors office in Vigan City, Ilocos Sur.
For his part, Ejercito described the case as mere harassment, saying it was meant to divert attention from his fathers trial for plunder in the Sandiganbayans Special Division.
Singson testified before the Sandiganbayan that Estrada demanded P130 million in kickbacks in exchange for the release of Ilocos Surs P200-million share of tobacco excise taxes.
Testifying for his own defense, Estrada denied Singsons claim.