A consumer group wants to keep Tony the Tiger from promoting sugary cereals on the SpongeBob SquarePants cartoon show, or anywhere else kids are watching.

The Center for Science in the Public Interest Wednesday announced legal action to try to stop the Kellogg Co. (K), maker of cereals like Frosted Flakes, and Nickelodeon cable network Viacom Inc., (VIA) from marketing junk food to children.

A planned lawsuit will ask a Massachusetts court to stop the companies from marketing junk foods in venues where 15 percent or more of the audience is under age 8, and to stop marketing junk foods through Web sites, toy giveaways, contests and other techniques aimed at that age group.

The planned lawsuit in Massachusetts is the latest attempt to use the courts to try to battle the growing obesity crisis in the United States.

A widely watched lawsuit filed in 2002 accused fast-food leader McDonald's Corp. (MCD) of using misleading advertising to lure children into eating unhealthy foods. McDonald's has called that lawsuit frivolous and parts of the case have been dismissed.

In the Massachusetts case, plaintiffs contend that the two companies are harming kids since the overwhelming majority of food products they market to children are high in items such as sugar and fat or nearly devoid of nutrients.

Of 168 ads for food that appeared on Nickelodeon during a review in the fall, 88 were for foods with poor nutritional quality, the center said. Nickelodeon characters like SpongeBob SquarePants were also used on packages of "junk foods" like Kellogg's Wild Bubble Berry Pop-Tarts, the center said.

Meanwhile, the center also reviewed 27.5 hours of Saturday morning programming and found 98 percent of the commercials promoted what it called "nutritionally poor foods."

"As a parent, I do my best to get my kids to eat healthy foods," Sherri Carlson, a plaintiff and mother of three, said in the center's news release. "But then they turn on Nickelodeon and see all those enticing junk-food ads."

Besides the Center for Science in the Public Interest, other plaintiffs in the case include the Boston-based Campaign for a Commercial-Free Childhood and Andrew Leong, a parent from Brookline, Massachusetts.

Massachusetts law requires that companies be given 30 days notice before a lawsuit is filed and the Center for Science in the Public Interest said it was giving that notice Wednesday.