Former President Rodrigo Duterte has expressed concern over the resurgence of the drug menace but is not keen on intervening in the current administration's anti-drug efforts, Senator Ronald "Bato" de la Rosa said Tuesday.

De la Rosa made the statement a day after he delivered a privilege speech saying drug syndicates are now "coming back with a vengeance."

He also mentioned the recent arrests of Philippine National Police and Philippine Drug Enforcement Agency officers in buy-bust operations.

"My privilege speech was part of our discussion and he was really sad that the drugs issue is recurring. He, however, doesn't want to interfere with how this government is running its own show. Ayaw niya (he doesn't want)," he said, in vernacular, in an interview with reporters.

De la Rosa, who served as PNP chief for one year and nine months during Duterte's administration, said the former president is likewise worried about the resurgence of "ninja cops" and "narco politicians" emphasizing that the children's future is again at stake.

"He was just expressing his concern that the ninja cops and narco politicians are now back and children are pitiful," he said as he echoed Duterte's concern on the drug problem.

De la Rosa then called for further intensifying internal cleansing in the ranks of the law enforcement agencies.

"I'm not saying that the police authorities and PDEA are remiss in their duties. They are doing their job but they should really intensify the fear factor," the senator clarified, adding that he will push for an investigation into the drug issues involving PNP and PDEA agents.