Producers are hoping to sign up the 40-year-old actress to play the head of a sinister organisation but are now worried she will turn down the role because she is reportedly dating Bond star Daniel Craig.
A source told The Sun newspaper: "Casting Rachel was going to be a surprise twist as everyone would assume she'd be a Bond girl when really she would play a villain.
"But The Fly in the ointment is that they are now dating."
The 23rd movie in the Bond franchise - reported to be called 'Red Sky At Night' - will see 42-year-old Daniel reprise his role as the suave British spy and is tipped to be "the biggest of all Daniel Craig's films", with bosses planning a death defying winter sports chase.
A Bond girl has yet to be announced.
Shooting will start later this year and its release will coincide with the 50th anniversary of the first Bond film, 'Dr No' in 2012.