Philippine President Rodrigo Duterte’s son has told a Senate inquiry he had no links to a seized shipment of $125 million worth of narcotics from China, dismissing as “baseless” the allegations of his involvement in the drugs trade.

Opponents of the President, who has instigated a fierce crackdown on a trade he says is destroying the country, say they believe his son Paolo may have helped ease the entry of the drug shipment at the port in Manila, the capital.

On Tuesday Duterte said he had told Paolo to attend the senate investigation if he had nothing to hide, besides advising him not to answer questions and invoke his right to keep silent.

“I cannot answer allegations based on hearsay,” Paolo Duterte, the vice mayor of the southern city of Davao, told the Senate.

“My presence here is for the Filipino people and for my fellow Davaoeños whom I serve,” he added, referring to the people of Davao, where his father served as mayor for more than two decades before being elected President in 2016.

The Philippine leader has repeatedly said he would resign if critics could prove any members of his family were involved in corruption.

Senator Antonio Trillanes, a staunch critic of the President, displayed to the Senate panel photographs of Paolo Duterte beside a businessman who was behind the shipment in which the alleged drugs were found.

The President’s son-in-law, Manases Carpio, who has also been accused of links to the May drug shipment from China, told the hearing he had no involvement.

​Duterte unleashed his bloody campaign the day he took office on 30 June last year, after promising Filipinos he would use deadly force to wipe out crime and drugs.

Police records show more than 3,800 people have died in police operations since July last year, and more than 2,100 other reported murders are linked to drugs.

Police reject activists’ allegations that they are executing suspected drug users and dealers and say officers shoot only in self-defence.

Trillanes said he had intelligence information from an undisclosed foreign country that Paolo Duterte was a member of a criminal syndicate, citing as proof a “dragon-like” tattoo with secret digits on his back.

Asked about the tattoo, Duterte said he had one, but declined to describe it, invoking his right to privacy.

Asked by Trillanes if he would allow a photograph to be taken of the tattoo and sent to the US Drug Enforcement Agency to decode secret digits, Duterte said: “No way”.

He refused to respond to questions about his bank accounts, calling them “irrelevant”.

The most controversial quotes from Rodrigo Duterte Show all 9 1 /9 The most controversial quotes from Rodrigo Duterte The most controversial quotes from Rodrigo Duterte On killing drug addicts “These sons of whores are destroying our children. I warn you, don’t go into that, even if you’re a policeman, because I will really kill you. If you know of any addicts, go ahead and kill them yourself as getting their parents to do it would be too painful” The most controversial quotes from Rodrigo Duterte Message to China “I will go there on my own with a Jet Ski, bringing along with me a [Phillipino] flag and a pole, and once I disembark, I will plant the flag on the runway and tell the Chinese authorities, ‘Kill me’ ” AP The most controversial quotes from Rodrigo Duterte Christmas message to law-breakers “If you do not want to stop, and just continue committing crimes, then this would be your last Merry Christmas” AP The most controversial quotes from Rodrigo Duterte On sex life “I was separated from my wife. I’m not impotent. What am I supposed to do? Let this hang forever? When I take Viagra, it stands up” AFP/Getty Images The most controversial quotes from Rodrigo Duterte On the drugs trade “None of my children are into illegal drugs. But my order is, even if it is a member of my family, ‘kill him'" AP The most controversial quotes from Rodrigo Duterte Insulting the Pope “We were affected by the traffic. It took us five hours. I asked why, they said it was closed. I asked who is coming. They answered, the pope. I wanted to call him: ‘Pope, son of a wh**e, go home. Do not visit us again’” AFP/Getty Images The most controversial quotes from Rodrigo Duterte Joke about rape “I saw her face and I thought, 'What a pity... they raped her, they all lined up. I was mad she was raped but she was so beautiful. I thought, the mayor should have been first” AFP/Getty The most controversial quotes from Rodrigo Duterte Insulting Barack Obama "Mr Obama should be respectful and refrain from throwing questions at me about the killings, or son of a bitch, I will swear at you in that forum" REUTERS The most controversial quotes from Rodrigo Duterte On Abu Sayyaf Islamic militants "If I have to face them, you know I can eat humans. I will really open up your body. Just give me vinegar and salt, and I will eat you. If you annoy me to the fullest... I will eat you alive. Raw" EPA

Presidential spokesman Ernesto Abella said the attendance of Duterte and Carpio “demonstrates that both gentlemen are willing and ready to face malicious allegations intended to impugn their character and credibility.”