NEW YORK (CNNMoney.com) -- A nutrition watchdog group is threatening to sue McDonald's if the fast-food giant won't stop using toys to lure children to its Happy Meals .

The Center for Science in the Public Interest said Tuesday that it has served McDonald's notice of its intent to sue over what it says is unfair and deceptive marketing.

is the stranger in the playground handing out candy to children," CSPI's litigation director, Stephen Gardner, said in a prepared statement. "It's a creepy and predatory practice that warrants an injunction."

In its notice letter, CSPI says that McDonald's toy-related promotions violate state consumer protection laws in four states and the District of Columbia. The letter gives

NEW YORK (CNNMoney.com) -- A nutrition watchdog group is threatening to sue McDonald's if the fast-food giant won't stop using toys to lure children to its Happy Meals .

The Center for Science in the Public Interest said Tuesday that it has served McDonald's notice of its intent to sue over what it says is unfair and deceptive marketing.

"McDonald's is the stranger in the playground handing out candy to children," CSPI's litigation director, Stephen Gardner, said in a prepared statement. "It's a creepy and predatory practice that warrants an injunction."

In its notice letter, CSPI says that McDonald's toy-related promotions violate state consumer protection laws in four states and the District of Columbia. The letter gives McDonald's 30 days to agree to stop the practice before a suit is filed.

The nutrition group claims that using toys to entice children instills bad eating habits and puts kids at higher risk of risk of developing obesity, diabetes, or other diet-related diseases over the course of their lifetime.