Mila Kunis has emerged as the frontrunner for the lead female role in the 'Fifty Shades of Grey' film.

The 'Black Swan' actress has been tipped to be cast as Anastasia Steele in the movie adaptation of the saucy novel after being crowned the Sexiest Woman Alive by men's magazine Esquire.

The 26-year-old brunette's girl-next-door charm has propelled her to the top of the list of actresses being considered to play the naïve female lead, who becomes lured into an S&M lifestyle by older billionaire Christian Grey.

'Harry Potter' star Emma Watson and 'Twilight' actress Kristen Stewart are also favourites to star in the big screen adaptation of E.L. James' erotic bestseller.

Ryan Gosling and 'The Vampire Diaries' star Ian Somerhalder are popular choices to play mysterious businessman Christian.

Meanwhile, Kelly Marcel - who was executive producer of cancelled TV sci-fi drama 'Terra Nova' - has been chosen to write the script for Universal and Focus Features' upcoming 'Fifty Shades of Grey' film. Michael De Luca and Dana Brunetti are on board to produce, reports.

Dana commented: ''We were all taken with the depth and passion of Kelly's engagement with the characters and world E.L. James has created and we knew she was the right person to augment our 'Fifty Shades' family.''

Michael added: ''Kelly's work demonstrates her flawless structural technique and passionate commitment to emotion, humour and depth of character, which is particularly visible in the celebrated screenplay for the upcoming 'Saving Mr. Banks'.''