MANILA - President Rodrigo Duterte sees no problem with his son, Davao City Vice Mayor Paolo Duterte, and son-in-law Manases Carpio, attending the Senate probe into the smuggling of illegal drugs into the country, especially if they are innocent.

“They should,” Duterte said Tuesday when asked about the decision of the two to attend the Senate Blue Ribbon Committee hearing set Thursday.

The President, however, refused to give any advice to his son as this would draw speculation from his and his family’s critics.

“I would leave it to the lawyers,” he said.

“He’s old enough to know. He can take care of his problem. I don’t speculate. I don’t give him advice. I just said ‘kung wala ka talagang kasalanan, bakit hindi ka pumunta doon?’” he added.

In a Senate hearing last week, customs fixer Mark Taguba had said the younger Duterte and his brother-in-law were "name-dropped" by individuals who paid "grease money" to Customs officials for the release of P6.4 billion worth of shabu from China, which was later seized in Valenzuela City.

But Taguba has since cleared the Vice Mayor and Carpio of any involvement in alleged corruption at the Bureau of Customs.

Senator Antonio Trillanes IV, one of Duterte's chief critics, said Tuesday he has evidence linking the President’s son to the narcotics trade.

"Kapag pumunta sila diyan, talagang ibubulaga ko sa kanila 'yung ebidensya laban sa kanila at magli-link sa kanila sa droga na ito," Trillanes told DZMM.

Duterte earlier called Trillanes' evidence "trash."

The President has repeatedly said he would resign if any of his children would be proven corrupt. Malacañang has meanwhile challenged critics to back their accusations with evidence.