Apparition Films / Promotional 1 / 10
Apparition Films / Promotional 1 / 10

Kristen Stewart was banned from "groping" Dakota Fanning during their on-screen kiss for the new movie "The Runaways," because her co-star was just 15 when they shot the steamy scene.

The pair puckered up for a same-sex smooch during the film, which tells the story of the 1970s rock group fronted by Joan Jett, played by Stewart, and Cherie Currie, played by Fanning.

RELATED: See more Kristen Stewart pics

And Stewart, 19, admits she was restricted by working practice regulations when they filmed the kiss, because Fanning was so young.

RELATED: Joan Jett opens up about "The Runaways"

She tells Access Hollywood, "She was 15, and I wasn't allowed to grope her. I'm actually not kidding, there are major restrictions that I don't remember (from) when I was younger."

She then stopped herself from spoiling the plot, adding: "I don't want to give anything way. It's a really passionate, hardcore scene ... It's just something that happened in their lives."

RELATED: K.Stew vs. Taylor Momsen's Emo Teen Queen Battle

"The Runaways" hits theaters April 9.