Philippine President Rodrigo Duterte vowed Wednesday to file an impeachment complaint against the head of the country's anti-graft body after she launched an inquiry into allegations that he has billions of pesos in undeclared funds in bank accounts.

Duterte was angered when the agency confirmed last month it was examining claims that he failed to disclose the full extent of his wealth in a mandatory asset declaration when he was mayor of a southern city prior to becoming president.

"In the end, they will discover, to their sorrow, there is no such amount," he said.

An impeachment complaint against Conchita Carpio-Morales, who heads the Office of the Ombudsman, the government's anti-graft agency, would be based on accusations of "selective justice" and the use of "falsified documents," the president said. Carpio-Morales is also the aunt of Duterte's son-in-law.

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Protesters burn an effigy of Duterte during a day of protest in Manila, Philippines, last month. Duterte was elected in 2016 on a populist platform and vowed to eliminate the thriving drug trade in his country, but his presidency has aroused claims of corruption and human rights violations. (Romeo Ranoco/Reuters)

The firebrand leader added that he wants Supreme Court Chief Justice Maria Lourdes Sereno removed from her position because she allowed herself to be used as a tool by his political opponents, who are conspiring to unseat him with this inquiry.

Duterte said Sereno, along with Carpio-Morales, colluded with members of the Liberal Party of the Philippines and with his rival, Senator Antonio Trillanes to discredit him. Duterte alleges Trillanes supplied Carpio-Morales with illegally acquired and stolen bank records.

Trillanes denied the president's latest allegations in an interview with reporters. "Mr. Duterte, do not avoid the issue of hidden wealth with this malicious allegation," he added.

'Mr. Duterte, do not avoid the issue of hidden wealth with this malicious allegation.' -  Senator Antonio Trillanes

Carpio-Morales's office did not respond to telephone calls from Reuters to seek comment.
 
In an earlier statement, her office said, "This office shall not be intimidated. We will nonetheless proceed with the 
probe as mandated by the constitution."

In the Philippines, the president, vice-president, supreme court judges, heads of constitutional agencies and the ombudsman can only be removed through impeachment on the basis of high crimes such as treason, bribery, corruption, betrayal of public trust and constitutional violations.
 
Duterte added that Sereno did not disclose government earnings of 30 million pesos ($588,000 US) for serving as a private lawyer in an airport arbitration case. Sereno already faces a pending impeachment case in Congress.
 
Sereno made no immediate comment, but her lawyers said they were ready to answer the complaint and prove she had not committed an impeachable offence.
 
The Liberal Party of the Philippines made no immediate comment when contacted by Reuters.