MANILA – The testimony of a Customs broker linking President Duterte's son, Davao City Vice Mayor Paolo Duterte, to an alleged smuggling syndicate needs to be supported by verifiable evidence, the President's spokesman said Wednesday.

In a Senate hearing on Tuesday on the smuggling of P6.4 billion worth of shabu from China, Customs broker Mark Taguba on Tuesday said he gave millions of pesos to Davao City Councilor Nilo “Small” Abellera Jr. and other members of the alleged “Davao Group” in exchange for letting shipments with illicit drugs and contraband slip past port inspections.

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The younger Duterte’s name was dragged into the controversy as he was supposedly close to Abellera.

Presidential Spokesperson Ernesto Abella said Taguba’s allegations need further evidence to back it up or it will just remain hearsay.

“Everything has to be vetted even if somebody makes some form of implication. It still has to be vetted, especially the witness. Is this a credible witness? There has to be a verifiable evidence, hindi lang basta hearsay,” Abella told reporters in a chance interview.

Taguba said he sought help from Abellera in January when the Bureau of Customs (BOC) issued alert orders for his shipments.

He said he gave Abellera an "enrollment fee" of P5 million in cash when they met in Davao City.

• READ: Broker claims Davao City exec got millions in 'tara'

For the next 3 months, Taguba said he paid P10,000 for every container that passed port inspections. He said he handed the fee -which could total P1 million per week- to a certain "Jack."

Taguba added that he trusted Abellera and Jack on the assumption that they were close to the President's son, Davao City Vice Mayor Paolo Duterte.

Abellera skipped Tuesday's Senate hearing for medical reasons.

Abella said Abellera should cooperate with the Senate investigation, even as he maintained that the President does not want to interfere in the ongoing congressional probe.

Senator Antonio Trillanes IV earlier said that he wanted Abellera to attend the investigation because Taguba and BOC Deputy Commissioner Gerardo Gambala have claimed the existence of the Davao Group.

The senator said 5 informants "working within Customs and those within the proximity of Customs operations" confirmed that "they’re well-aware of the Davao Group."

"The question is, why would a councilor from Davao City be dealing with some brokers? This Small Abellera is known in Davao City to be very close to Paolo Duterte," Trillanes said.