WASHINGTON — Are the toys in your child's Happy Meal making him fat?

The Center for Science in the Public Interest says they are. The Washington-based consumer advocacy group threatened Tuesday to file a lawsuit against McDonald's, charging that the fast food chain "unfairly and deceptively" markets the toys to children.

"McDonald's marketing has the effect of conscripting America's children into an unpaid drone army of word-of-mouth marketers, causing them to nag their parents to bring them to McDonald's," CSPI's Stephen Gardner wrote to the heads of the chain in a letter announcing plans to file a lawsuit.

The center, which has filed dozens of lawsuits against food companies in recent years, is hoping the publicity and the threat of a lawsuit will force McDonald's to negotiate with them on the issue. The group announced the lawsuit in a letter to McDonald's.

McDonald's Vice President of Communications, William Whitman, said in a statement that the company "couldn't disagree more" with CSPI's assertion that their toys violate any laws. He said McDonald's restaurants offer more variety than they ever have and Happy Meals are made smaller for kids.

"We are proud of our Happy Meal which gives our customers wholesome food and toys of the highest quality and safety," Whitman said. "Getting a toy is just one part of a fun, family experience at McDonald's."

CSPI says the suit would be filed in state court. The center has not settled on a state yet, but the group believes the toys in Happy Meals violate state consumer protection laws in Massachusetts, Texas, the District of Columbia, New Jersey and California.

McDonald's has fought such criticism for years, and the company made a pledge in 2007 to advertise only two types of Happy Meals to children younger than 12: one with four Chicken McNuggets, apple dippers with caramel dip and low-fat white milk, or one with a hamburger, apple dippers and milk. They both meet the company-set requirement of less than 600 calories, and no more than 35 percent of calories from fat, 10 percent of calories from saturated fat or 35 percent total sugar by weight.