A mother-of-two from California launched a class-action lawsuit against McDonald's, claiming the toys given out with Happy Meals unfairly lure kids into eating unhealthy food.

Monet Parham is spearheading the suit backed by the Center for Science in the Public Interest (CSPI), aimed at stopping the fast-food giant's use of toys in marketing aimed directly at small children.

The CSPI says such marketing illegally exploits children. Parham says the main reason her six-year-old daughter, Maya, asks to go to McDonald’s is to get toys based on Barbie, i-Carly, Shrek, or Strawberry Shortcake.

"I am concerned about the health of my children and feel that McDonald’s should be a very limited part of their diet and their childhood experience," said Parham, from Sacramento.

"But as other busy, working moms and dads know, we have to say 'no' to our young children so many times, and McDonald’s makes that so much harder to do.

"I object to the fact that McDonald’s is getting into my kids’ heads without my permission and actually changing what my kids want to eat."

The CSPI cited the Institute of Medicine and the American Psychological Association as saying that "kids as young as Maya do not have the cognitive maturity to understand the persuasive intent of advertising."

"Every time McDonald’s markets a Happy Meal directly to a young child, it exploits a child's developmental vulnerability and violates several states' consumer protection laws," said CSPI litigation director Steve Gardner.

McDonald's said it would defend itself against the lawsuit, which Parham and the CSPI said they were filing in the California Superior Court in San Francisco.

"We are proud of our Happy Meals and intend to vigorously defend our brand," spokeswoman Bridget Coffing told the LA Times newspaper, adding that Happy Meals offer quality foods in smaller portions appropriate for children.

"We are confident that parents understand and appreciate that Happy Meals are a fun treat, with quality, right-sized food choices for their children that can fit into a balanced diet," she added.

The action came after San Francisco last month agreed to ban promotional toys served with food that doesn't meet strict nutritional standards, following a similar move in nearby Santa Clarita in April.