Kristen Stewart and Robert Pattinson are locked in a bitter custody dispute over their dog.

The couple adopted Bear together from a high-kill shelter in New Orleans but after Kristen cheated on Robert with her 'Snow White And The Huntsman' director Rupert Sanders, the furious actor moved out of their shared Los Angeles home and denied her access to the pooch.

A source told RadarOnline: "After Rob moved his things out of their Los Angeles apartment, he then told Kristen he wanted Bear.

"She was heartbroken - they adopted Bear together and she always felt that he was their little baby.

"But Rob was so hurt by Kristen's actions he decided that he wants the dog to help him get over what happened. After all, a dog is a man's best friend and Bear is such a good companion.

"However, Kristen won't give up Bear in a hurry. She helped Rob save Bear from Parvo disease [a highly contagious disease which causes death in 91 per cent of cases when left untreated], which nearly took its life when it was a puppy.

"She wants joint custody - and it could get a little messy."

Before news of Kristen's fling was revealed, the couple had been planning to adopt a second puppy.

The source added: "Robert and Kristen were looking into the possibility of adopting another dog. They were desperate for a play pal for Bear and scoured petfinder.com, as well as a few high-kill shelters in Los Angeles. But it seems that's out of the question now."