Australian actress Rebel Wilson has contacted police over allegations her name and image have been used to promote a weight loss product without her permission.

The Pitch Perfect star was alerted to an online promotion which allegedly suggested she uses a pumpkin-shaped fruit from Indonesia to lose weight, and included 'before and after' snaps.

In a message to a follower, Wilson writes, "This is some scam, I have no idea what that is or why they are using my image," before warning all her fans, "Hey guys, just to be clear, if you see an ad for some weight loss product with my name and picture on it, it is 100 per cent not me. Some bs (bulls**t) scam!"

Wilson goes on to confirm she has alerted police to the situation, adding, "Hey everyone, especially friends in Australia, if you see a post about me relating to some 'diet' product: this is a Scam. Police alerted... They are unlawfully using my name and image. Please ignore."