President Rodrigo Duterte

MANILA – President Rodrigo Duterte on Wednesday slammed the former president of Colombia for criticizing his war on drugs, calling him an "idiot."

Cesar Gaviria, who led Colombia's bloody narcotics crackdown and battled drug kingpin Pablo Escobar, said in a New York Times opinion piece that violence is not the way to win the war on drugs.

"[The former president of] Colombia has been lecturing about my [war on drugs]...that idiot," Duterte said, without mentioning Gaviria by his name.

The Former South American leader urged Duterte to reconsider his bloody crackdown despite its popularity in the Philippines.

"Throwing more soldiers and police at the drug users is not just a waste of money but also can actually make the problem worse. Locking up non-violent offenders and drug users almost always backfires, instead strengthening organized crime," the former South American leader said.

Duterte should instead strengthen public health programs, safeguard human rights and focus on economic development, Gaviria said.