PRESIDENT Rodrigo Duterte on Wednesday hit out a former Colombian president's criticism of his deadly war against illegal drugs.

In a speech delivered at the 115th founding anniversary of the Bureau of Customs in Port Area, Manila, Duterte called former Colombian President Cesar Gaviria idiot after he claimed that the Philippine President was repeating the "same mistake" in his approach to prevent drug abuse.

Gaviria was President of Colombia from 1990 to 1994 and the secretary general of the Organization of American States from 1994 to 2004.

In an opinion piece published by the New York Times, Gaviria told Duterte that "there will always be drugs and drug users in the Philippines."

He said that improving public health and safety, strengthening anti-corruption measures, and investing in sustainable development are alternative ways for Duterte to suppress narcotics trade.

"I was also seduced into taking a tough stance on drugs during my time as president. The polls suggest that Mr. Duterte’s war on drugs is equally popular. But he will find it unwinnable," said Gaviria.

Duterte, however, shrugged off Gaviria’s recommendation and stressed that the drug problem in the Philippines was worse than Colombia's.

He cited that Colombian people are merely using cocaine and heroin, which he said are somehow not dangerous for public consumption.

Duterte otherwise said that Filipinos using shabu could make their brains "shrink" if they take it for a year because it is a "virulent chemical."

"They said, Colombia has been lecturing about [drug war]. That idiot," Duterte said.

"You know, they are using cocaine. Cocaine and heroine, not really [dangerous to public]. Cocaine and marijuana, those are somehow okay. You can still communicate. But shabu, They are mixing battery water. The fact alone that you would mix battery water would give you indication something about your brain," he added.

The President then maintained that his fight against drugs would continue.

"I promise that I will try to suppress drugs. I have been receiving so many lectures and communications and criticisms, but you know, if we do not control drugs and it has reached the four million, [it will ruin the country]," Duterte said. (SunStar Philippines)