NEW YORK - A children's advocacy group wants the Department of Health and Human Services to oust Shrek, the animated ogre, from his role as spokesman for an anti-obesity drive.

The Campaign for a Commercial-Free Childhood says soon-to-open Shrek the Third has too many promotional ties with unhealthy foods to justify using Shrek as a health advocate.

"There is an inherent conflict of interest between marketing junk food and promoting public health," Susan Linn, the group's director, wrote in a letter sent yesterday to HHS Secretary Michael Leavitt.

The character, said Linn, an instructor in psychiatry at Harvard Medical School, "is a walking advertisement for McDonald's, sugary cereals, cookies and candy."

HHS spokesman Bill Hall said the department had no intention of halting the public-service ads, which were launched in February and seek to curtail childhood obesity.

The ad campaign is a joint project of HHS, the Ad Council's Coalition for Healthy Children, and DreamWorks Animation SKG, creator of the three Shrek movies. It features ads in which Shrek, a stout and often clumsy ogre, and his fellow characters urge children to exercise at least an hour a day.

"Shrek is a very well-known character in the target population," Hall said, adding that a healthy diet "does not necessarily exclude the occasional treat."

Linn's organization - a nationwide coalition which monitors marketing aimed at children - said Shrek the Third, which opens May 18, had promotional deals with dozens of food products, including Mars Inc.'s Snickers and M&M's candy; PepsiCo Inc.'s Sierra Mist drink; and Kellogg Co.'s Froot Loops, Frosted Flakes, Pop-Tarts, Cheez-Its and Keebler cookies.

The film also has a tie-in with McDonald's; there will be Shrek-themed promotions of Happy Meals, and DreamWorks will create animation for some McDonald's commercials.

"Why would young children follow Shrek's advice about healthy living and ignore his entreaties to eat Happy Meals and Pop-Tarts?" Linn wrote. "If government agencies are serious about combating childhood obesity, they should stop cozying up to industry and start taking real steps to end the barrage of junk food marketing aimed at children."