Naomi Lloyd, presenter of ITV's West Country breakfast bulletin, told viewers that the large, white beast had been brought in on the tide close to the seaside town of Bude.
"A walker in Cornwall has caught an extraordinary sight on camera. A polar bear has washed up on a beach near Bude," said Lloyd.
"The bear comes from the Arctic Circle and an investigation is under way as to how it could have ended up there."
However, the animal was subsequently identified as a cow that had been bleached white by the sea water, reports The Daily Telegraph.
ITV dropped the story from later bulletins and acknowledged the "embarrassing" mistake, but insisted that it was an easy one to make.
"The animal caused quite a stir in Bude. Several people has seen the animal from a cliff top and thought it was a polar bear," a spokesman said.
"Its size and colour and its lying position on the beach did make it look like a polar bear and we had several calls.
"But on closer inspection we discovered it was a cow. The tide was very strong and it did bring several dead animals in along that stretch of coast."
The animal was first spotted by dog walkers early yesterday morning, who immediately contacted the television stations.
The British Divers Marine Life Rescue (BDMLR) service, which also received calls about the incident, said: "Mostly we deal with stranded seals, whales, dolphins and porpoises. We don't get calls about polar bears in Cornwall all that often. Or cows, for that matter."