The Staffordshire bull terrier cross was found by a member of the public on Wednesday morning, wrapped in a duvet in a black Adidas sports bag.
The dog was rushed to The Stubbington Ark RSPCA Animal Shelter but died before arrival.
The charity has published a video of the dog after it was found, showing how it had become riddled with fleas.
To watch the clip click on the video at the top of the page.
Overgrown nails and a small growth were also some of the signs of neglect found by vets at the centre.