MANILA - (UPDATE) Dangerous Drugs Board Chairman Dionisio Santiago has tendered his irrevocable resignation Monday.

Executive Secretary Salvador Medialdea relayed Duterte's instruction for Santiago to step down, citing the DDB chairman's comment that a mega drug rehab facility was a ''mistake."

• READ: Mega drug rehab center in N. Ecija a 'mistake': DDB chief

Asked for comment on the instruction to resign, Santiago told ABS-CBN News: "Malacañang knows best. The boss is always right."

Before he was told to resign, Santiago sought Duterte's approval for a strategy plan to combat narcotics.

In November 1, during an interview with ANC's Headstart, Santiago said money for the Mega Treatment and Rehabilitation Center in Nueva Ecija could have been used to fund smaller community-based rehabilitation programs.

The rehab center was a key project under Duterte's war on drugs built in partnership with philanthropists.

"That was a mistake. Ang problema, naging excited si President. Yung ginasta doon, puwedeng ginamit sa mga community based rehab yun, malilit which can only accommodate siguro mga 150 to 200," he told ANC's Headstart.

• What to see at PH's newest mega drug rehab facility

Santiago, former head of the Philippine Drug Enforcement Agency, said admitting drug dependents to the treatment center must have been difficult due to its location.

Duterte also fired Santiago's predecessor Benjamin Reyes for contradicting him on the number of drug dependents in the country.

The President said there were 4 million Filipinos addicted to drugs when Reyes said there 1.8 million drug addicts.