R&B beauty Rihanna has slammed a U.K. tabloid report suggesting she used a body double in a sexy new advertisement for Armani underwear.

The "Umbrella" hitmaker recently stripped off to shoot the revealing black and white commercials, in which the singer writhes around in bed before waking up and pulling on some jeans.

However, editors at Britain's The Sun newspaper claim the sexy close-up shots of Rihanna's butt and cleavage are actually those of Irish model Jahnassa Aicken, who had reportedly signed a gag order to ban her from discussing the job.

An insider tells the publication, "Jahnassa's torso, body and bum appear in parts of the ad. It's shocking Rihanna wanted one considering she loves posing with no clothes, plus she's in great shape."

But Rihanna insists the tattoo on her hand proves the curves shown in the black and white ads are all hers and she has lashed out at The Sun in a series of angry Twitter.com posts.

She writes, "Ok @thesunnewspaper, this is the only way I could say this to you!!! F--- YOU... Who is Jahnassa... Does she have a tat (tattoo) on her hand too?"