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She's been called the hottest girl in the world, but according to Shia LaBeouf, Megan Fox wasn't ready to become a sex symbol when Transformers hit theaters in 2007.

"Megan developed this Spice Girl strength, this woman-empowerment [stuff] that made her feel awkward about her involvement with [director] Michael Bay, who some people think is a very lascivious filmmaker, the way he films women," LaBeouf, 24, tells The Los Angeles Times.

"Mike films women in a way that appeals to a 16-year-old sexuality. It's summer. It's Michael's style. And I think [Fox] never got comfortable with it," he explained. "This is a girl who was taken from complete obscurity and placed in a sex-driven role in front of the whole world and told she was the sexiest woman in America. And she had a hard time accepting it."

As a result, Fox, 25, was replaced by supermodel Rosie Huntington-Whiteley in the series' third installment, Transformers: Dark of the Moon.

"Rosie comes with this Victoria's Secret background, and she's comfortable with it, so she can get down with Mike's way of working and it makes the whole set vibe very different," LaBeouf said.