Fox, 24, became an international sex symbol thanks to her role as Mikaela Banes in the films about shape-shifting machines doing battle.

Paramount Pictures said it had declined the option of using Fox for part three in the blockbuster trilogy directed by Michael Bay.

Studio insiders indicated that Bay wanted to take the story line in a different direction and to cast another actress as star Shia LaBeouf’s love interest.

However, Fox said it was her decision not to return for the third film and that she “wished the franchise all the best”.

Fox, notorious for making provocative comments to the media, engaged in a public spat with Bay around the release of part two last summer. Bay later defended her and said he looked forward to working with her on part three.

In an interview last September, she said of Bay: “He wants to be like Hitler on his sets, and he is. So he’s a nightmare to work for, but when you get him away from set, and he’s not in director mode, I kind of really enjoy his personality because he’s so awkward.”

Fox was subsequently branded “dumb as a rock” by members of the Transformers film crew, who were believed to be behind an anonymous posting on the internet in which she was described as a “thankless, classless and graceless” idiot better suited to a career as a porn star.

At the time, Bay said: “I don’t condone the crew letter to Megan. And I don’t condone Megan’s outlandish quotes. But her crazy quips are part of her crazy charm.”

In announcing Transformers 3 last October, Bay wrote on his blog: “P.S. Megan Fox, welcome back. I promise no alien robots will harm you in any way during the production of this motion picture.”

The first two Transformers films have made more than $1.5 billion (£1 billion) worldwide.

Production on the third instalment begins this month with a release date of July 1, 2011.