The show's creator made the accusation at the monthly comedy event Harmontown in Los Angeles recently, reports TMZ.
Harmon explained of the incident that sparked the feud: "I had written a very simple scene that Chevy couldn't possibly f**k up."
He alleged to a packed audience that when Chase objected to the scene, the writer refused to back down as he had an emotional attachment to the material, causing Chase to exit the set without completing the scene.
Although the actor later tried to reconcile by sending a text message, Harmon revealed how he reacted: "I said, 'F**k you... you breached your contract, you're an asshole'."
He went on to tell the audience: "And then what happened a day later? That night... after what I'm guessing is two bottles of Beaujolais. Ladies and gentleman... Chevy Chase," before playing the voicemail to the crowd.