Olivia Munn poses nude for PETA

Iron Man 2 actress Olivia Munn has become the latest celebrity to pose in the buff for animal rights group PETA.

Munn's nude hoarding attacks the circus for its treatment of elephants, specifically those employed by the Ringling Brothers and Barnum & Bailey.

"When you look at something like the circus and everyone's laughing and there's colour and there's music and everything seems so great," Fox News quoted her as saying in a commercial also released by People for the Ethical Treatment of Animals.

"But when you go right behind that door and they're in these crates all day long and then they're getting shocked and beat just so they can get up and dance around on a ball... it was just so sickening," she said.

PETA is, however, increasingly drawing criticism for its gratuitous use of nudity in its campaigns and for allegedly spending money to sign up celebrities instead of actually helping animals.

A writer on one celebrity news and gossip website remarked, tongue firmly in cheek, that such campaigns may only encourage people to tether a few more elephants in the hope of seeing some more celebrities take their kits off.