The U.S. Center for Science in the Public Interest (CSPI) is suing Quorn Foods and Whole Foods Market over what it calls a dangerous food additive.

The center, which wants a Texas court to require warning labels on Quorn packages and on Whole Foods' freezer cases, has been urging the Food and Drug Administration (FDA) and the Federal Trade Commission (FTC) to more closely regulate Quorn and its retailers.

The center also wants its suit to be certified as a class-action case.

Quorn, sold in Britain since 1995, was introduced in the U.S. in 2002 as a healthy alternative to meat. Its packaging calls the main ingredient "mycoprotein," which the label describes as being related to mushrooms, morels and truffles.

However, the center says mycoprotein is made from a fungus and is more akin to mildew than mushrooms. It says companies grow this fungus in giant vats, harvest it and process it to resemble chicken or ground beef.