MANILA – Senator Leila de Lima has filed a resolution seeking a legislative probe into the alleged bribery incident involving officials of the Bureau of Immigration (BI) and gambling tycoon Jack Lam.

“There are too many nagging questions that necessitate a deeper independent probe by the Senate. We cannot just entrust such investigation to DOJ/NBI (Department of Justice/National Bureau of Investigation) which are both under [Justice Secretary Vitaliano] Aguirre's control. It's like entrusting a wolf to guard the sheep," De Lima said in a statement.

The BI was recently rocked by a scandal involving two of its deputy commissioners, Al Argosino and Michael Robles, two fraternity brothers of President Rodrigo Duterte who were accused of receiving P50 million from Lam through his alleged representative, former policeman Wally Sombero.

• READ: Two Duterte frat brods figure in corruption scandal

The bribe money was supposedly for the release of 1,316 illegal Chinese employees arrested at Lam's Fontana Leisure Park and Casino at Clark Freeport in Pampanga.

Argosino and Robles said they only kept P30 million of the full amount as evidence in their intelligence operation against Lam.

They said the remaining P20 million went to Sombero and BI intelligence chief Charles Calima, who got P2 million and P18 million respectively.

Argosino and Robles claimed Calima took P18 million of the P50 million bribe "for distribution" to other immigration officials.

They have since been sacked by no less than President Rodrigo Duterte and are now facing plunder charges.

Calima has turned over the P18 million to the Criminal Detection and Investigation Group (CIDG) while Sombero surrendered the P2 million to the Office of the Ombudsman.

Prior to this bribery scandal, Aguirre claimed that Lam, through Sombero, attempted to bribe him.

De Lima, a former justice secretary who also supervised the BI, raised several questions on the developments involving the Lam bribery case, such as Aguirre’s “seeming lackluster response” on the bribery attempt.

• READ: Aguirre won't sue over gambling tycoon's alleged bribe try

"If indeed Lam, through his middleman Wally Sombero, attempted to bribe Aguirre, why didn't the latter effect right then and there, a warrantless arrest of Sombero, the latter being in flagrante delicto, and thereafter promptly move to prevent Lam's departure or escape from the country?" she said.

"This failure in law enforcement and immediate prosecution of Jack Lam and his cohorts has led the public to speculate on the real story behind this incident," De Lima added in her resolution.

De Lima, a staunch critic of Duterte and his bloody war on drugs, also accused the president of handling the sacked BI officials with kid gloves.

"This failure in law enforcement and immediate prosecution of Jack Lam and his cohorts has led the public to speculate on the real story behind this incident," she said.

"(This) bribery scandal raises issues on the seriousness and/or capability of the government to enforce its anti-corruption laws in situations where those involved are personal friends of the appointing authority.”

In her resolution, De Lima said the investigation in aid of legislation aims to “enhance the principle of command responsibility in bribery and corruption cases by penalizing negligence in the enforcement of laws on bribery and corruption, especially the negligence of top investigation and prosecution officers.”