MANILA (Reuters) - The Philippine Supreme Court began hearing arguments on Tuesday on a government bid to invalidate the appointment of the court's top judge, whom President Rodrigo Duterte is calling an "enemy" who needs to be removed.
Chief Justice Maria Lourdes Sereno's fellow high court judges will decide on merit of arguments for and against a petition, referred to as a "quo warranto", by the government's chief lawyer, for alleged violations in the appointment process.
The embattled judge, the Philippines' first woman chief justice, is facing challenges on several fronts and is on a leave of absence to prepare for possible impeachment proceedings.
Duterte makes no secret of his dislike of Sereno.
Sereno appeared at a Supreme Court session in the city of Baguio, to defend herself against Calida's petition.
Dozens of her supporters, holding streamers and denouncing some of the judges, held a protest outside the court. Nearby, anti-Sereno protesters called for her resignation.
Sereno has voted against several of his controversial proposals, including extending martial law on a restive island and allowing late dictator Ferdinand Marcos to be buried in a cemetery for national heroes, but Duterte denies instigating two attempts to remove her.
Sereno has until now refrained from blaming Duterte but directly questioned his intentions in a speech on Monday.
"Mr President, if you have no hand in this, why did Solicitor-General Jose Calida, who reports to you, file the quo warranto?", she asked.
"Surely, you must explain this unconstitutional act".
Within a few hours a furious Duterte lashed out at Sereno and indicated he was ready to use his influence over the legislature to get rid of her.
"I'm putting you on notice that I'm your enemy and you have to be out of the Supreme Court," he told reporters before heading to an Asian leaders' forum in China.
"I will see to it. And after that, I will request Congress go to the impeachment right away."
The nearly 300-seat house returns from a recess next month and will convene for a plenary vote on the impeachment complaint, which accuses Sereno of failure to fully declare her earnings.
If passed, an impeachment trial will be conducted in the upper house, with the 22 sitting Senators as judges.
A spokesman for Sereno said she was eager to prove in court she had done nothing wrong.
(Reporting by Manuel Mogato; Editing by Martin Petty, Robert Birsel)