The world's most famous fast-food chain has a major public-relations problem on its hands.

That's because several animal-welfare groups have banded together to take on McDonald's, according to a new video created by Mercy For Animals. 

The controversy revolves around how the company's suppliers raise poultry used in Chicken McNuggetts.

The video maintains that many of these chickens have been bred to grow four times as quickly as similar animals in the 1950s.

"If humans grew as fast as they do, we would be 660 pounds by the time we were two months old," the video states. "In other words, McNuggetts are made from Frankenchickens."

Mercy For Animals states that this extra weight causes these chickens to suffer intensely, "just as a 600-pound human baby would".

Last October, McDonald's announced eight "commitments to advancement in chicken welfare".

They include partnering with tech companies, producers, and suppliers to enhance on-farm monitoring systems, as well as sourcing chickens "raised with improved welfare outcomes".

There are also pledges to provide a minimum six hours of darkness during 24-hour periods and sourcing chickens in North America at operations that use controlled atmospheric stunning.  

Mercy For Animals, however, calls this a "skimpy, weak policy that fails to provide chickens the most basic protections that dozens of other companies have pledged to offer them".