"The warlords are profiting from the political agreement for peace and reconciliation in Central African Republic," they wrote, referring to a February 2019 agreement.
The rebel leaders were enjoying full freedom of movement and impunity despite the fact that they were continuing their operations on the ground, they added.
The February 2019 peace accord between the government and 14 rebel groups has failed to bring security back to most of the country.
The country is still prey to the activities of rebel groups since a coalition of armed groups overthrew president Francois Bozize's regime in 2013.
The bishops also criticised the government for failing the public, but expressed hope that the army, rebuilt with the help of the European Union and Russia, would be able to re-establish state authority across several provinces.
Former president Bozize is one of those running in the December presidential election, a high-risk vote in one of the world's poorest countries, which has been plunged into civil war since he was overthrown in 2013.
Central African Republic is a predominantly Christian country.