MANILA (Reuters) - Philippine President Rodrigo Duterte’s allies in Congress on Tuesday filed a criminal complaint against a senator who has been an outspoken critic of a surge of extrajudicial killings unleashed by the president’s campaign against drugs.

Former Justice Secretary and current Senator Leila De Lima shows reporters her personal mobile phone during a news conference at the Senate headquarters in Pasay city, metro Manila, Philippines September 22, 2016. REUTERS/Romeo Ranoco

The legal complaint against Senator Leila de Lima, who was justice minister in a previous administration, is the latest government action against her since she led an inquiry into the killings.

She has denounced the government attacks on her as “madness” and “harassment” and she has appealed to Duterte to stop the string of bizarre accusations and insults.

Senators loyal to Duterte ousted her from the leadership of the investigation in September.

Congressmen then accused her of disrespect in connection with criticism she made of her treatment and the fate of the inquiry. That led to a criminal complaint.

“Senator de Lima has shown disrespect to the House of Representatives,” said Congressman Reynaldo Umali, head of the lower house’s justice panel.

“We cannot allow this incident to pass, how can we earn the respect of the people when a senator insults us by calling the inquiry a sham and a kangaroo court.”

De Lima is on an official trip to the United States and Europe and was not available for comment.

Duterte’s war on drugs, the key plank of his campaign for a May election, has claimed about 5,000 lives since July 1.

The high toll and mysterious circumstances of some of the killings have alarmed rights groups, the United States and United Nations, whose concerns have drawn angry rebukes from Duterte.

Umali said de Lima faced imprisonment of up six months if found guilty.

A small group of opposition politicians in Congress said the case against de Lima would have a chilling effect on critics of Duterte’s war on drugs.