MANILA, Philippines — Accusing Ombudsman Conchita Carpio Morales of having mastered “the art of selective justice,” President Rodrigo Duterte warned her on Tuesday that her hold on office is “very, very precarious.”

Duterte slammed Morales for her alleged bias in handling complaints in her office, saying that the ombudsman was soft on friends and hard on enemies.

The chief executive warned Morales, whose brother is Sara Duterte Carpio's father-in-law, that her hold on office is legally flimsy since she was just supposed to serve out the remainder of the term of former Ombudsman Merceditas Gutierrez, who resigned even before her impeachment trial could proceed in the Senate in 2011.

“That it has not been questioned until now, I do not know why,” the president said in a speech before newly-appointed government officials.

The president claimed that Morales has not been able to live up to her constitutional mandate.

“[The Office of the Ombudsman] cannot act on complaints with a cold neutrality of an impartial tribunal which is basically required in due process,” Duterte said. “It seems that the Office of the Ombudsman has mastered the art of selective justice, harsh on some, soft on others, even when they all suffer from similar and analogous circumstances, slow to act on complaints against the friendly, but quick to decide against perceived hostiles.”

Duterte said that it is not too late for Morales to be without fear nor favor in dispensing justice, advising the ombudsman to follow a saying that he said he has always abided by.

He said: “When I took my oath of office on June 30, 2016, I said that one principle of governance I abide with in running the affairs of my administration is contained in the saying, ‘I have no friends to serve. I have no enemies to harm. I am beholden to no one save my conscience.’”

Duterte said he detests the alleged bias of the Office of the Ombudsman in dealing with cases before it.

“The lack of moral courage to do what is right and act beyond those two twin failings ends up in inequitable decisions. Scratch my back, and I’ll scratch yours is how some people describe it. It is to me detestable,” he said.

The tension between Duterte and Morales has risen in recent months after the ombudsman criticized the president for encouraging the killing of suspected drug suspects.

Then, Duterte announced the police and soldiers should seek his permission first before appearing in any of the probes of the anti-graft agency.

Morales said about this: “Anong pakialam niya? Under the law, we have subpoena powers. We have orders for particular officials including police and soldiers to show up or to file pleadings. If they don't file pleadings, that's their lookout.”

In March, the Supreme Court junked a disbarment complaint against Morales filed by former Manila councilor Greco Belgica, a known Duterte supporter.

The Volunteers Against Crime and Corruption also warned Morales of an impeachment case if she clears Aquino of multiple murder charges in connection with the 2015 Mamasapano clash that left more than 60 people dead.

READ: Aquino faces charges for role in Mamasapano clash