President Gloria Macapagal-Arroyo earlier said that Mendoza and National Security Adviser Lisandro Abadia were De Villa’s recommendees.
De Villa hurled the challenge to anti-crime crusaders Carina Agarao and Teresita Ang-See who have questioned Mendoza’s appointment.
Agarao, who heads the Crusade Against Violence (CAV), alleged that Mendoza aided the killer of her husband, human rights lawyer Clarence Agarao.
On the other hand, Ang-See, who leads the Citizens Against Crime and Corruption (CACC), claimed that Mendoza was unfit to head the PNP because of his "tainted" track record, being a "compulsive gambler."
De Villa confirmed in an interview over radio station dzRH that he met Agarao and Ang-See last week.
He said he urged the two women to file formal complaints against Mendoza, if they have "real evidence," instead of hurling accusations through the media.
He added that he would even ask the Department of Justice to initiate an investigation, if the need arises.
"If the results of the investigation show that cases must be filed, so be it. Immediately, we will relieve him (Mendoza) the next day," he said.
De Villa added: "I told them if you gave the former PNP chiefs a chance, why don’t you give Larry (Mendoza) a chance, too."
He also defended the appointment of Abadia, whom former Defense Secretary Orlando Mercado pinpointed as the reason why he quit the Arroyo Cabinet.
Mercado said he could not work with Abadia whom he had indicted for fund mismanagement at the AFP Retirement and Separation Benefits System (RSBS).
"We listen to all complaints but we have to put them through the process and not just allow such accusations being thrown our way. We must move forward and advance in what we are doing," he said.
Abadia, also in an interview over dzRH, lashed back at Mercado who, he said, has been "obsessed" with the RSBS case.
"I will hang on to my position and I will clear myself. These allegations were made after my appointment. I just want to vindicate myself," he said.
Abadia said he had warned Mrs. Arroyo beforehand that Mercado would likely revive the allegations against him despite the fact that the Ombudsman never investigated him nor required him to file a counter-affidavit.