Former president Rodrigo Duterte will be sued for grave threat raps by ACT Teachers Partylist Rep. France Castro, whom he threatened to kill over issues of confidential funds requested by his daughter, Vice President Sara Duterte.

Castro said the criminal complaint is scheduled to be filed tomorrow morning before the Quezon City Regional Trial Court with some National Union of Peoples Lawyer members, former Philippine Bar Association head Rico Domingo, and lawyer Antonio La Viña, who volunteered to handle the case.

"This is a crime against a person. Former president Duterte's threats should stop," she said in an interview on Monday.

The progressive lawmaker has been on the receiving end of Duterte's tirades following the crusade of the Makabayan bloc to strip the VP of multi-million confidential funds from the proposed 2024 budget.

VP Duterte sought P500 million and P150 million in confidential funds for OVP and the Department of Education, respectively.

The militant group waged a successful battle against the VP's secret funds as the House leadership concurred with their proposal of formally removing it and rather channeled it to agencies in charge of monitoring and protecting the country's national security and territorial rights in the West Philippine Sea.

The VP, who claimed her secret funds will be used to promote peace and order, previously accused critics of having "insidious motivations."

The OVP and DepEd, which the VP concurrently heads, were among the three civilian agencies, namely the Department of Agriculture, the Department of Foreign Affairs, and the Department of Information And Communications Technology, awarded zero confidential funds for next year.

The former president said Castro would have been the "first target" of his daughter's intelligence fund.

"It's time for the Dutertes to stop doing this, especially former president Rodrigo Duterte. He admitted he kills. So, it has to be stopped because it has no place in this society," Castro said.

According to Castro, she only did her duties as a lawmaker of scrutinizing the budget, particularly the confidential funds, and the Dutertes should not interpret it as a personal affront.

House leaders previously said they would not tolerate Duterte's threats and intimidation of any members of the lower chamber. Moreover, they would back Castro's move to file legal action.

The House is also geared up to provide Castro additional security following a death threat from Duterte, according to House secretary general Reginald Velasco.