Emma Watson wardrobe malfunction makes a costume boob at her Hollywood premiere

LA: Emma Watson suffered an embarrassing costume boob at the Hollywood premiere of her new movie last night. After waltzing down the red carpet in an elegant full-length backless lace dress, Emma's left breast slipped out from her glamorous gown.

Only a perfectly-placed nipple cover protected the 22-year-old's modesty, until she spotted the wardrobe malfunction and adjusted her outfit.

It was a minor hiccup on a triumphant night for Emma - who has finally completed her transformation from Harry Potter's feisty heroine Hermione Grainger to full-blown Hollywood starlet.

The actress pouted for the cameras, saving her smiles for the hundreds of fans who waited for hours outside the ArcLight Cinerama Dome on Los Angeles' Sunset Boulevard.

Her devoted followers were rewarded with autographs and the chance to chat with the stunning star as she promoted The Perks Of Being A Wallflower.

Those lucky enough see her up close couldn't fail to notice her flawless pale skin, complemented by subtle make-up and a simple slicked-back hairdo.

Earlier in the day Emma asked Twitter followers to come along and support the film, offering tickets to a lucky few.

She tweeted: "If you guys have a free hour at 6:30 come to the Cinerama Dome Sunset Boulevard and celebrate the Hollywood Premiere of 'Perks'. C u there!

"I think we have 10 tickets to give away to the movie...."

In the film, Emma plays a high school student who finds love with a shy classmate, played by actor Logan Lerman.

And it's winning rave reviews.

After a rousing reception at the Toronto Film Festival at the weekend, Emma proudly tweeted: "Did I tell you we got a standing ovation in Toronto Film Festival ? : ) #perks"