Pimentel rallied behind his PDP-Laban partymate and Makati City Mayor Jejomar Binay who along with his wife Elenita and nine others were charged with graft before the Office of the Ombudsman for alleged anomalous purchases worth P232 million.
It was not the first time that Pimentel has spoken out against Malacañangs alleged action on its critics through the filing cases against them with just a few months left until elections.
Binay was previously directed by the legal office of Malacañang to respond to a complaint by former Makati City Vice Mayor Roberto Brillante that he was allegedly hiring ghost employees.
Brillante, a long-time political foe of Binay, was also behind the present graft case filed against Binay.
"Its a sad day for justice when the Arroyo administration selectively prosecutes mayors opposing her like Mayor Binay," Pimentel said.
"No matter what the excuse, the message is clear. Those who oppose her beware," he added.
Earlier, Pasay City Mayor Wenceslao Trinidad was suspended by the Office of the Ombudsman on the basis of an ongoing investigation into an alleged anomalous garbage collection contract.
"It seems there is a game plan to cripple the opposition so that the opposition mayors will not be in office come election time," Pimentel said.
In the case of Binay, Pimentel said that the mayor was an easy target since he was spearheading anti-Arroyo movements as the president of the United Opposition.
Pimentel said that while the administration is going after the opposition local chief executives, it is deliberately overlooking pro-administration counterparts who are also facing graft charges.
"It seems what they are enforcing is selective justice. Whoever they want to go after, they will do it," Pimentel said.
According to the senator, if Binay is suspended for six months like Trinidad, he would no longer be sitting in office when the election period starts.
"In other words, that is the policy that Mrs. Arroyo seems to be pursuing. They are using scare tactics. They warn mayors critical of the President to be careful with what they are doing because they may be the next to be suspended," he said.