"Community" star Chevy Chase BLASTED the show's creator on a SCATHING voice mail for the guy ... telling Dan Harmon he's a "g*dd*mn a-hole" who sucks at writing.
The voice mail is FEROCIOUS ... and according to reports, it's the boiling point in a raging feud that's been going on behind the scenes of the show for months.
During the voice mail, Chase calls Harmon a "g*dd*mn bad writer ... s**t ... stink-o" ... and adds, "Your writing is getting worse and worse."
He also calls Harmon a "fat f**k" who will probably die soon because he eats like crap.
Chase also makes reference to an incident that went down at the show's wrap party, when Harmon allegedly led the crowd in a "F**k You Chevy" chant ... in front of the actor's wife and daughter.
Sources tell TMZ, the rant was extremely awkward for everyone present -- some people joined in, but most people just watched uncomfortably. And Chevy stormed out.
The chant was reportedly in response to Chase walking off the set on one of the final days of shooting.
We reached out to both camps for comment -- so far, no response from either side.