The Corrections Officers’ Benevolent Association will kick off attacks against Mayor de Blasio on Thursday for the spike in city jail violence during his tenure.

The union is planning to distribute 50,000 palm cards throughout the five boroughs slamming Hizzoner for being “last in the nation for ‘safe jails.’”

“Although the number of inmates in the city’s jails may be down, the violence in jails continues to rise and it shows no sign of declining,” the flyer says.

De Blasio has also come under fire from the union for supporting the recently released Lippman Commission report, which calls for the eventual closure of Rikers Island.

“Since Mayor de Blasio has refused to listen to our grave concerns about the 18 percent increase in jail violence, we’re taking our message directly to registered voters across the city,” said COBA President Elias Husamudeen.