Metro Manila (CNN Philippines) — The first impeachment complaint against President Rodrigo Duterte was filed on Thursday, just eight months after he assumed presidency.

Magdalo party-list Representative Gary Alejano filed the 16-page complaint before the House of Representatives' Office of the Secretary-General.

Alejano said the President should be impeached on the following grounds:

Culpable violation of the Constitution

Engaging in bribery

Betrayal of public trust

Graft and corruption

Other high crimes

Article 11, Sec. 2 of the 1987 Constitution says the President and other government officials "may be removed from office on impeachment for, and conviction of, culpable violation of the Constitution, treason, bribery, graft and corruption, other high crimes, or betrayal of public trust."

The impeachment complaint is based on allegations of illegal acts supposedly committed by Duterte both as President and as then mayor of Davao City.

Alejano said Duterte is "not fit to serve as President" and "should be held liable for the crimes he committed."

Presidential Spokesman Ernesto Abella said the move against the President seems like an outline for a destabilization plot against the administration.

"It does seem like part of a larger scheme of things… with acts of trying to discredit the administration and trying to throw it in doubt," Abella said.

Related: Defense Chief: No destabilization plot vs. Duterte

Alejano said the Magdalo party-list has no plans to oust Duterte through a coup d'etat or any other extra-legal means.

Before being a member of the "Magnificent 7" minority bloc of the House of Representatives, Alejano was a former marine captain who was among the leaders of the 2003 Oakwood Mutiny, a failed attempt to oust then President Gloria Macapagal Arroyo.

Alejano admits having Duterte ousted through impeachment proceedings is an "uphill battle" amid the overwhelming force of the majority.

But he is confident the impeachment complaint will get the support it needs from other members of the Congress.

According to the Constitution, a vote of at least one-third of the members of the House of Representatives, or 98 out of the 292 incumbent congressmen, can start an impeachment trial at the Senate.

He added several lawmakers have already expressed their support in the impeachment complaint against the President, but he refused to disclose their names.

Bloody drug war

The impeachment complaint said Duterte, in the conduct of his bloody drug war, violated the Constitution, betrayed public trust, and committed bribery, murder and other high crimes.

The President in his public pronouncements "ordered, instigated, and/or induced" the policemen to kill suspected drug users and even offered cops promotion or pardon in case they are convicted due to extrajudicial killings, Alejano said.

In the process, Duterte has "undermined the integrity of his office" and has "brought disrepute to the Presidency," thus betraying public trust, Alejano added.

More than 2,500 drugs suspects were killed in police operations in the country's anti-drug campaign. Human rights groups have alleged that the number of deaths has reached 7,000.

Also read: PNP: 23 dead in 1st week of renewed drug war

Abella, in response, reiterated that there are no state-sponsored killings. "The President has made sure that he will not turn a blind eye on all uniformed personnel who violate and abuse their power."

Also read: PNP chief promises better drug war enforcement

DDS

The impeachment complaint also wants Duterte ousted from power over his alleged involvement in the killing of more than 1,400 people in Davao City as supposed leader of vigilante group Davao Death Squad.

It is based on the testimonies of self-confessed Davao Death Squad leader, retired SPO3 Arthur Lascañas and self-professed hitman Edgar Matobato. Lascañas and Matobato told the Senate they killed people in Davao City upon the orders of then Mayor Rodrigo Duterte.

Also read: Lascañas in affidavit: Matobato was telling the truth

Alejano said although these were committed before Duterte assumed the presidency, he should still be held liable for his "crimes."

Duterte has repeatedly denied forming and leading the Davao Death Squad. He recently admitted the group's existence in Davao City in the 1970s, not to kill criminals, but to combat communist rebels.

Graft and corruption, treason?

Duterte also violated Republic Act 3019 or the Anti-graft and Corrupt Practices Act both as President and as Davao City Mayor, Alejano said.

He said then-mayor Duterte conducted an "anomalous" hiring of 11,000 contractual workers in Davao City, whom Matobato and Lascañas said were also death squad members.

This cost local government coffers P708 million, Alejano said, quoting a 2015 report from the Commission on Audit.

The complaint also included as basis for impeachment Senator Antonio Trillanes' claims that Duterte held P2.207 billion in alleged unexplained wealth in undisclosed bank accounts. Trillanes has yet to provide official evidence of the bank accounts.

Trillanes also said Duterte has over 40 undisclosed properties. These, along with the alleged P2.0 billion may have been "unlawfully acquired" by the President and his family, Alejano said.

Duterte has denied the allegations and even ordered the Anti-Money Laundering Council (AMLC) to release information on his net worth.

Alejano said they also wanted to include in the impeachment complaint Duterte's supposed treason over his "secret agreement" with China which apparently allowed Chinese ships to survey Benham Rise.

He said his team is studying the issue, and might file a supplemental complaint in the coming days.

The Palace has denied any such "secret agreement." "There was no exclusion, there was no conflict," said presidential spokesperson Abella, adding that the President would be open to disclosing the written agreement to the public.

Duterte also earlier said the Philippines will assert the country's rights over resource-rich Benham Rise, but through diplomacy

CNN Philippines' Joyce Ilas contributed to this report.