Metro Manila (CNN Philippines, October 26) — The Justice Department says its hands are tied on drug allegations against two stalwarts of the opposition Liberal Party (LP).

Justice Secretary Vitaliano Aguirre on Wednesday said he has been receiving questions about the October 18 affidavit of drug suspect Ricky Serenio, who accused Senate Minority Leader Franklin Drilon and former LP President Mar Roxas of protecting drug lords in the Visayas, along with Iloilo City Mayor Jed Mabilog.

Aguirre said the information must be forwarded to the Philippine Drug Enforcement Agency (PDEA), since it has been tasked by no less than President Rodrigo Duterte to lead the war on drugs.

Read: Duterte gives PDEA lead role in drug war

"It's up to PDEA to take whatever action they want to take," Aguirre told reporters in a press briefing on Wednesday.

He said the Justice Department, including the National Bureau of Investigation, may not be allowed to launch a probe on the issue.

Serenio is a self-confessed bagman for the Berya Drug Ring, a drug syndicate operating on Negros Island.

In an affidavit on October 18, he stated that Drilon and Roxas wanted to "penetrate the illegal drug market in the entire Negros Island." He added that it was the late Melvin Odicta, an alleged top drug lord in Western Visayas, who told him in 2015 of Drilon and Roxas' plans.

Related: Alleged Iloilo drug lord Melvin Odicta, wife shot dead

The LP in a statement on Thursday called Serenio's affidavit a "baseless testimony" and hit the Duterte administration for propagating lies.

"This latest drug allegation against prominent members of Partido Liberal clearly proves that this administration is going all-out to demonize the party in the eyes of the public and to divert attention from the pressing problems of the country, such as rising prices, extrajudicial killings, and corruption, including drug smuggling at the Bureau of Customs," the LP said.

Malacañang refused to speculate on the controversy.

"Antayin nalang natin na may talagang dumating kaganapan ng panahon at para makita natin kung talaga namang may laman 'yang sinasabing 'yan," Presidential Spokesman Ernesto Abella said Tuesday when asked about Serenio's statements.

Translation: "Let's just wait for an event that will prove if his statements really has weight."

The LP likened the Serenio allegation to the situation of their fellow partymate, Senator Leila de Lima, who has been detained on drug charges "due to testimonies of convicted criminals serving jail sentences." De Lima has been accused of abetting the illegal drug trade in the national penitentiary during her term as justice secretary.

President Duterte has called Iloilo the "most shabulized" province in the country, with the Iloilo City Mayor also named on his list of narco-polticians.