Senator Leila de Lima on Monday said she will not be intimidated by threats of a possible lawsuit after she pushed for a Senate investigation on the alleged summary executions of drug suspects all over the country.

Asked about Solicitor General Jose Calida's statement that he is studying the filing of a case against de Lima, the senator said: "Ano ikakaso nila? That I am also involved in drugs? Hindi na ako magtataka that they will label me as a protector or coddler of drugs."

De Lima said there are "telltale signs" that some of the drug suspects being killed by law enforcers are victims of summary executions.

"Nakakaduda yung explanation na nanlaban, nang-agaw..." she said.

She also wondered why Calida was ordering police not to attend the proposed Senate investigation on the killings.

"Why is there such a reaction? If they are confident na sinusunod lahat ng dapat sundin, bakit ganyan ang reaction?" she said.

She added: "I will not be intimidated, I will still push for my proposal to conduct a Senate inquiry unless overruled by my colleagues."

President Rodrigo Duterte has vowed a bloody campaign against the drug menace, saying police officers will receive protection from government if they eliminate drug lords nationwide.

He earlier singled out De Lima for failing to solve the drug problem, saying incarcerated drug lords were cooking meth inside the national penitentiary during De Lima's watch.

Calida echoed Duterte's statements on Monday and said police officials could snub Senate investigations being conducted "in aid of media mileage."

In response, De Lima denied that a meth laboratory was operating inside the New Bilibid Prison during her time as justice chief. "Imposible ho yun unless lahat magkakakuntsaba," she said.

She also criticized Calida for telling police that they could snub the congressional inquiry and that a complaint must be filed first before the Senate can investigate any issue.

De Lima said the Senate inquiries on the January 2015 Mamasapano operation, the P10 billion PDAF scandal and the dispersal of farmers in Kidapawan were all conducted prior to the filing of a complaint.

"Ngayon ko lang narinig yan na dapat may complaint before calling for a Senate inquiry...Why insist now on the prior filing of a complaint when it is not in the rules? There is also precedence," de Lima said.

De Lima, who has butted heads with Duterte in the past, denied that she is an obstructionist to the Duterte administration's policies. She said she favored Duterte's push for peace talks and the passage of a freedom of information law as well as the creation of a superbody to investigate media killings.

She said the inquiry is meant to help strengthen the government's fight against the drug menace "without sacrificing human rights and without the law enforcers breaking the law."