House Speaker Pantaleon Alvarez's impeachment threat against Vice President Leni Robredo is the "reaction" of a "sleeping giant" for launching a jab against the ruling party's chairman, Senate President Aquilino "Koko" Pimentel said Tuesday.

Hours after Magdalo Party-list called for President Rodrigo Duterte's impeachment, Alvarez said he is looking at filing impeachment raps against Robredo for criticizing the government's war on illegal drugs in a video that was shown during a United Nations meeting.

"Reaction na lang 'yun kasi may nag-file against our chairman, siyempre nagising . . . ang ginising n'yo sleeping giant pa," said Pimentel, who is also the president of Duterte's PDP-Laban.

Pimentel hinted that it may be easier for Alvarez's complaint to gain traction in the lower chamber since the impeachment process is a numbers game.

"It is theoretical . . . But what I know of is that the Speaker has 230-plus followers in the House of Representatives. From party mates alone, he has 109. It is more than the threshold number of 100," Pimentel said referring to the required one-third vote from the House members to push the impeachment case to the Senate.

"Sinong unang nanuntok? Napa-react tuloy si Speaker and he has the numbers. That's the problem. Ang ginising ninyo sleeping giant," Pimentel added.

Even though the Palace also tagged Robredo's allies from the Liberal Party in an alleged destabilization plot against Duterte, Pimentel denied that the president was involved in the impeachment brawl between lawmakers.

"Si presidente actually ay hands off . . . It's the Speaker's original idea . . . Para siyang nagising doon sa pag-file," Pimentel said.

The Senate president earlier challenged the Liberal Party to "denounce" the impeachment complaint against Duterte to prove that they are not involved in the alleged plot to unseat the president.