Kidman, 45, recreated Sharon Stone's "Basic Instinct" moment by opening her legs to flash at a death row inmate as she pants and writhes in her chair, reported Sun online.
In the film, the ex-wife of Tom Cruise plays oversexed housewife Charlotte Bless, who exchanges love letters with a convict.
The Oscar-winning actress stars alongside Efron, Matthew McConaughey and John Cusack.
Based on the novel by Lee Dexter, the film follows a newspaper reporter (Efron) who has returned to his home town to investigate Van Wetter's (Cusack) case in a bid to prove he is innocent but soon becomes involved with Kidman's character, who is writing to the convict.
The film premiered at the Cannes Film Festival in May and has attracted attention for its adult content and themes.