Jessica Alba has threatened to sue Playboy after an unauthorised picture of her was used on the cover.

The Sin City star was asked by the publication to pose for the cover after she was told that she ranked very highly on a reader poll of the sexiest celebrities. Alba's publicist refused the photo shoot, but did allow the magazine to use a publicity photo from Columbia Pictures on the stipulation that it be used inside the magazine.

However the March edition of Playboy features Jessica Alba in a bikini on the front next to the words "25 Sexiest Celebrities". Alba's lawyers are claiming that this is a cynical attempt by the magazine to boost sales by implying that the edition contains explicit pictures of the actress.

"In featuring Ms. Alba's photograph on the cover of Playboy's March issue, it is clear that Playboy's intent was to create a false belief and/or expectation among the public that Ms. Alba voluntarily appeared in the nude, or semi-nude and that a revealing pictorial of her is contained in Playboy's March issue," Jessica’s attorney stated.

In using the picture without her consent, Alba says that the magazine may have caused "immeasurable harm" to her reputation and career, and that she is seeking legal council over the matter.