The Liberal Party on Tuesday criticized Senate President Aquilino "Koko" Pimentel for challenging members of the opposition to "denounce" the impeachment case filed against President Rodrigo Duterte.

"Hindi kami ang nasa likod nung impeachment complaint ngunit hindi rin kami mga tutang sunod-sunuran," Liberal Party president Francis "Kiko" Pangilinan said in a statement.

(We are not behind the impeachment complaint but we are also not puppies who will just follow orders.)

• READ: LP denies hand in Duterte impeachment: 'Baseless, orchestrated lies'

Pimentel, in a press conference held Monday, urged members of the Liberal Party to condemn the impeachment case to prove that they are not part of an alleged destabilization plot against the President.

"If they are really not behind this impeachment, they should denounce the impeachment against Duterte, denounce the people behind the impeachment against Duterte," Pimentel earlier said.

Pangilinan slammed the Senate president for assuming that he is in a position where he can dictate what other lawmakers should do.

"Who is he to tell us what to do? Hindi lang siya ang halal na senador," he said.

(Who is he to tell us what to do? He is not the only senator elected by the people.)

Duterte's legislative allies have tagged Vice President Leni Robredo and her party mates as the mastermind behind the impeachment complaint filed by Magdalo party-list Rep. Gary Alejano against the chief executive.

House Speaker Pantaleon Alvarez has threatened to file an impeachment complaint against Robredo for betrayal of public trust after she criticized Duterte's war on drugs in a video played during a United Nations meeting.

Pimentel said there is no need for Duterte to denounce the impeachment against Robredo to prove that he is not involved with Alvarez's threat.

"Si Presidente actually ay hands off... It's the Speaker's original idea," Pimentel said.