A photo that appears to show Miley Cyrus engaging in a sex act has been dismissed as a fake by her representatives.

The shocking snap has been circulating online, prompting rumours the teen star has been caught up in another photo scandal - a year after she posed virtually nude for celebrated photographer Annie Leibovitz.

Pictures of her in her underwear have also surfaced on the internet, as well as snaps that appeared to show her mocking Asians.

But her rep has acted swiftly, insisting the new photo, which appears to show Cyrus performing oral sex on an unidentified male, is a fake.

The spokesperson says, "The alleged photo of Miley Cyrus circulating the internet is completely fabricated."