Actor Shia LaBeouf has issued an abject apology after being accused by comic book writer Daniel Clowes of using his work uncredited for LaBeouf's latest film as director, the short film Howard Cantour.com which premiered at Cannes.

The issue came to light after the short debuted online on 16 December, after which it became apparent that LaBeouf had included dialogue from Clowes' story Justin M Damiano, which, like LaBeouf's Howard Cantour.com, is a study of a world-weary and disillusioned film critic.

Speaking to Buzzfeed, Clowes said: "The first I ever heard of the film was this morning when someone sent me a link. I've never spoken to or met Mr. LaBeouf … and I was shocked, to say the least, when I saw that he took the script and even many of the visuals from a very personal story I did six or seven years ago and passed it off as his own work. I actually can't imagine what was going through his mind." The film, starring Jim Gaffigan, has since been taken down and replaced with a trailer.

LaBeouf issued a stream of increasingly apologetic tweets. "Copying isn't particularly creative work. Being inspired by someone else's idea to produce something new and different IS creative work.... In my excitement and naiveté as an amateur filmmaker, I got lost in the creative process and neglected to follow proper accreditation.... Im embarrassed that I failed to credit @danielclowes for his original graphic novella Justin M. Damiano, which served as my inspiration... I was truly moved by his piece of work & I knew that it would make a poignant & relevant short. I apologize to all who assumed I wrote it ... deeply regret the manner in which these events have unfolded and want @danielclowes to know that I have a great respect for his work... I fucked up."

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