An opposition lawmaker filed an impeachment complaint in the Philippine Congress on Thursday against President Rodrigo Duterte, calling for his removal for what he said were high crimes, betrayal of public trust and abuses of power.

Lower house representative Gary Alejano accused Duterte of offences he said were worthy of impeachment, from concealing assets and conflicts of interest, to drug-related extrajudicial killings and running an alleged “death squad” when he was mayor of Davao city.

Duterte has rejected similar allegations levelled at him in the past. His spokesman on Thursday said Alejano was trying to create doubts among the public about the administration.

Alejano said his aim was to give Filipinos a chance to speak up against a powerful president.

“Our goal with this complaint is to be a vehicle for Filipinos to have a voice to oppose and fight against the abuses and crimes of President Duterte,” Alejano told a televised news conference.

“We know it’s an uphill battle … but we believe that many will support this complaint.”

He said Duterte’s actions were a “culpable violation of the constitution, engaging in bribery, betrayal of public trust, graft and corruption and other high crimes“.

Alejano accused Duterte of having a state policy of killing drug offenders.

More than 8,000 people have been killed since Duterte unleashed his anti-drugs crusade, some 2,500 in police raids and sting operations. The authorities vigorously deny involvement in thousands of mysterious killings of drug users.

Presidential spokesman Ernesto Abella said the complaint was part of a wider plot by opponents to undermine the Duterte administration.

“It seems rather dramatic that everything seems to be so coordinated at this stage,” Abella told reporters.

“It looks like they’re scraping the bottom of the barrel.”

Alejano accepted he may have difficulty getting house support behind his impeachment bid. Duterte’s popularity rating remains high and he enjoys big support in the bicameral Congress.

“We know the numbers are against us and we are facing a big challenge,” Alejano said.

“But we still believe that impeachment would be fought not only inside the halls of Congress but also outside.

“There’s the church, schools, civil society and the many Filipinos who did not vote and do not support and not in favour of the policies under President Duterte.”