Kristen Stewart was banned from "groping" Dakota Fanning during their onscreen kiss for 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, about the 1970s rock group and featuring the "Twilight" actress as Joan Jett and Fanning as her band mate Cherie Currie.

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

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. I don't want to give anything way. It's a really passionate, hardcore scene."

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