Whedon, who came aboard last year to write, direct and produce the film, said he 'failed' to come up with a good story.
"'Batgirl' is such an exciting project, and Warners/DC such collaborative and supportive partners, that it took me months to realise I really didn't have a story," he told The Hollywood Reporter.
Referring to DC president Geoff Johns and Warner Bros. Picture Group president Toby Emmerich, he added, "I'm grateful to Geoff and Toby and everyone who was so welcoming when I arrived, and so understanding when I.uh, is there a sexier word for 'failed'?"
The 53-year-old is best known to comic book fans for writing and directing Marvel's 'The Avengers' and 'Avengers: Age of Ultron', though he also came in to finish DC's 'Justice League' after Zack Snyder was forced to step away from the film following a family tragedy.
Whedon also created the hit TV series 'Buffy the Vampire Slayer' and 'Agents of S.H.I.E.L.D.', among others. (ANI)