Clues about moviemaker Michael Bay's decision to leave the Transformers world behind have been revealed in a leaked email to Paramount studio bosses.

Bay has stepped down as the director of the film franchise, starring Shia LaBeouf, after two movies, insisting he has "had enough" of making big budget blockbusters.

But a new memo, sent to movie bosses and obtained by TMZ.com, suggests he was unhappy with the way his Transformers sequel was being promoted.

The email to Brad Pitt's former production partner and Paramount boss Brad Grey, dated 4 May, 2009, reads, "I have been waiting, and waiting for the anticipation of an 'event movie' to make it into the public zeitgeist."

Bay calls the print campaign for Transformers: Revenge of The Fallen an "abject failure" and insists the promotion of the movie at the recent MTV Movie Awards was "so lame".

He asks, "Is this is a cash issue with your company?"

It appears either Bay has since reconsidered his comments or Paramount bosses have appeased him with a boosted publicity campaign - because in another leaked email, written earlier this month, the director praises Grey and the studio executives, writing, "Paramount is like family. Thank you all for busting your butts and bringing your 'A game' for the release of Transformers."

The email was a farewell of sorts - last week, Bay announced he would not be making a third Transformers film.

He said, "After the three and a half years I've spent making these movies, I feel like I've had enough of the Transformers world. I need to do something totally divergent, something without any explosions."