A suggestive advertisement showing Rihanna writhing around in her underwear features shots of a butt and body double, The Sun reports.
The pop sensation is seen in the Armani ad having a nightmare in bed before putting on a pair of jeans.
But shots that appear to show Rihanna, 24, in her underwear showing her chest and butt are in fact model Jahnassa Aicken.
Rihanna's management insisted that the Irish Aicken, 27, sign an order banning her from talking about the job.
But a source said, "Jahnassa's torso, body and bum appear in parts of the ad."
The source added, "It's shocking Rihanna wanted one, considering she loves posing with no clothes -- plus she's in great shape."
The Belfast-based Style Academy agency booked Aicken, who received a "modest sum" for the shoot. She was first spotted by Rihanna's people in a crowd during shooting of the star's "We Found Love" video in Northern Ireland. They used her as a stand-in before she was cast in the Armani ad.
A spokesman from the Advertising Standards Authority, the UK's independent regulator of advertising, said, "If we have complaints consumers have been misled by the use of a body double, we will investigate."