Lennon was attending a book launch to publicise his mother CYNTHIA's memoirs of marriage to the IMAGINE hitmaker when he launched his attack.
And he saved his fiercest criticism for her contribution to the critically-panned Broadway musical LENNON.
He says, "I haven't seen it but I read some reviews and thought, what a mess.
"The way she describes his life to the world is in connection with her."
Musician Julian also claims the artist has denied him some of his father's most treasured possessions, as well as the domain name www.johnlennon.com for which he battled her in court.