Defending his decision to replace Anthony with his son Wolfgang, Van Halen told the new issue of Billboard magazine his former bassist lacked musical ability, claiming he had to teach the rocker every note for tours.
Van Halen added, "Every note Mike ever played, I had to show him how to play. Before we'd go on tour, he'd come over with a video camera and I'd have to show him how to play all the parts."
The comments have irked Hagar, who still performs with Anthony in Chickenfoot, and, in a video message to fans posted on his Facebook page, he rages, "It's really irritating to see them going after Mikey. Mikey didn't do anything, ever, to Van Halen. Mikey was the most loyal guy in the band. He was the first guy there at rehearsal, the last guy to leave, the first guy at the gig.
"I was in that band for 11 years. There was never a video camera involved of Eddie showing him what to play. Eddie would tell him what to play once in a while and say, 'No, Mike. Don't play that many notes. Just stay on one note so that I can f**k up and nobody will know it.' It was that kind of s**t.
"I'm telling you straight up, especially on the '04 reunion tour. If Mike would have played any more than one note, it would have shown that Eddie wasn't playing the right chords again and again and again. I couldn't sing to him. You couldn't play bass to him. So that is a lot of bulls**t and I don't know why they go after him like that. He doesn't deserve it.
"Michael Anthony is a bad motherf**ker. F**k you, EDDIE VAN HALEN for saying that about Mikey. You're a liar... I'm so p**sed about that... Michael Anthony is the greatest guy on the f**king planet."
Meanwhile, Anthony has taken the high road in the dispute, stating, "I am proud to say that my bass playing and vocals helped create our sound. I've always chosen to take the high road and stay out of the never-ending mudslinging, because I believe that it ultimately ends up hurting the Van Halen fans."