Celebrities such as Paris Hilton who pose for pictures with primates have been branded "chumps with chimps" by a United Nations body.
Hotel heiress Paris and other stars including Khloe Kardashian and Real Madrid footballer James Rodriguez have shared photographs online showing themselves cuddling apes, often at private zoos.
Doug Cress, of the UN's Great Apes Survival Partnership (Grasp), has warned that such images are damaging efforts to stop wildlife trafficking and are even endangering the survival of some species.
He told the Press Association: "The Great Apes Survival Partnership wants celebrities who pose for photos with chimpanzees or orangutans and broadcast those images around the world to know that simple act can have a devastating impact on conservation.
"You might say Paris Hilton can't know better, or Conan O'Brien can't know better, or James Rodriguez can't know better - but that's no excuse.
"They're chumps with chimps, and they should know better, particularly when they are followed by millions of fans online."
Cress said studies have shown that the general public cares less about conservation and senses less urgency for endangered species when it sees them treated "like dolls or toys or playthings".
He added: "We stop seeing them as wild animals. They become pets. We demean them. The potential for donations goes down, the commitment to change lessens... it's a real knock-on effect."
He said a celebrity holding an orangutan on Instagram can drive the illegal trade, as the perceived value of a "pet" orangutan then goes up.
"A few selfish, thoughtless moments from a celebrity can undermine efforts to save orangutans, chimpanzees, gorillas, bonobos and other endangered species," he said.