Rodrigo Duterte lashed out at Senator Leila de Lima, who is conducting an inquiry into the sudden surge of extrajudicial killings coinciding with the president's new war on drugs.
In a speech Wednesday, Duterte denounced de Lima in starkly personal terms.
Speaking to police officers and dignitaries, including former President Fidel Ramos and Chinese Ambassador Zhao Jianhua, Wednesday at a ceremony marking the 115th anniversary of the Police Service, Duterte called Senator Leila de Lima an "immoral woman" and alleged that she used her driver -- also her lover, Duterte said -- to collect drug payoffs on her behalf.
He called de Lima, one of his biggest critics, a "robber" who was using her driver to collect drug money during May's election campaign.
"In fairness, I would never say here that the driver gave the money to her. But by the looks of her she has it," he said.
"Here is an immoral woman fronting, the wife of the driver was concerned," he alleged. "Here is a woman who funded the house of her lover."
While he did not refer to de Lima by name in that address, he later confirmed during a speech
at Manila's airport that he was indeed referring to the lawmaker.
De Lima told reporters that she found his comments to be "foul" and that they amounted to character assassination.
"We are both professionals, the president and I... I hope he doesn't resort to those foul means. To me, that's very foul," local media reports her saying, days before Senate hearings on Duterte's war on drugs are set to begin.
"A lot of bleeding hearts, including senators of the republic, are complaining about the death rate in the fight against drugs," Duterte said in the speech at Camp Crame, the Philippine National Police headquarters, in Quezon City on the outskirts of Manila.
He reiterated that his officers had the right to use deadly force in self-defense.
"If the resistance is violent thereby placing your life in jeopardy, shoot and shoot him dead. Can I be more clear than that?"
On Thursday, de Lima added in a statement that the attack from the "highest official of the land" had left her feeling powerless.
"No one has ever been attacked in such a manner by no less than the highest official of the land, until now," the statement reads.
"How does one defend oneself, when the attacker is immune from suit, and has all the backing of executive power to support him in his personal attack?"
De Lima has long been an opponent of Duterte, and as head of the Commission on Human Rights under the former administration, attempted to tie Duterte to involvement in the infamous Davao Death Squad, a paramilitary vigilante organization in his hometown of Davao, where he served as mayor for over two decades.
The Philippine Daily Inquirer's "Kill List,"
regarded as one of the most accurate records of the killings of suspected drug dealers in police engagements and by vigilantes, recorded the deaths of 693 people suspected of drug crimes between June 30, the day Duterte assumed office, and August 15.
De Lima also called Duterte's recent actions and statements, "use and abuse of power" and vowed to continue the senate hearings to protect innocent victims of extra-judicial killings and help strengthen the rule of law.
De Lima has summoned Philippine National Police Chief, Director-General Ronald "Bato" de la Rosa -- a longtime ally of the president -- along with human rights groups, lawyers and families of victims to testify.
A statement from the president's office said that he "has taken umbrage with de Lima's approach, of not only taking the moral high ground with regard to drug-related deaths, but her assumptions that said deaths are directly attributable to (the) war on drugs," and said that his opponent was using the situation to "grandstand."
A presidential spokesman also added that the attack should not be construed as a warning against those who question the government's anti-drug campaign.