For decades, advertising to children on television has been held to tougher rules than commercials for adults. Federal regulators have long been concerned that kids are more vulnerable to marketing and have a tougher time distinguishing between an ad and a show.

Now with new apps, such as YouTube Kids, hosting videos aimed at children,the same rules aren't being applied, opening up children to more advertising than ever before, according to a group of children's advocacy and public interest groups. In a complaint to be filed to the Federal Trade Commission on Tuesday, the groups alleged YouTube Kids, owned by Google, contains a host of videos created by McDonald's, Fisher Price, American Greetings and other companies aimed at getting children to buy their products.

On the American Greetings' Strawberry Shortcake channel, for instance, a 37-second video features the red-haired doll describing the company's "Food Fair" app, where characters pick ingredients for recipes. At the end, a banner appears showing the app can be downloaded on iTunes. McDonald's has a 7-minute video dispelling myths about the contents of Chicken McNuggets. On another video, a deep-voiced announcer warns, "All vegetarians, foodies and gastronauts, kindly avert your eyes," with a slow-cam close up of a juicy Big Mac. "You can't get juiciness like this from soy or quinoa."

YouTube Kids is aimed at families looking for convenient, free children's programs. Launched in February, YouTube explained, the service would have extra protections for families by filtering out mature content that can easily find its way into a search on the regular site. YouTube also explained on its advertising guidelines that it would not permit the advertising of food products or apps.

Advertising of "products related to consumable food and drinks are prohibited, regardless of nutrition content," the guidelines stated.

YouTube said it disagrees with many of the contentions by the consumer groups.

"When developing YouTube Kids we consulted with numerous partners and child advocacy groups," the company said in a statement. "While we are always open to feedback on ways to improve the app, we were not contacted directly by the signers of this letter and strongly disagree with their contentions, including the suggestion that no free, ad-supported experience for kids will ever be acceptable."

McDonald's and other companies label its sponsorship of videos, but child development experts and consumer advocacy groups say young children often can't tell the difference between videos that are presented as entertainment or educational and those that are commercial advertising.

“In today’s digital era, children deserve effective safeguards that will protect them regardless of the screen they use,” said Jeff Chester, executive director of the Center for Digital Democracy, one of several groups filing a complaint to the Federal Trade Commission that the app violates children's advertising rules. Other groups include the Campaign for a Commercial-Free Childhood, the American Academy of Child and Adolescent Psychiatry, the Center for Science in the Public Interest, Children Now, the Consumer Federation of America, Consumer Watchdog and Public Citizen.

Chester said the FTC needs to update rules to explicitly include advertising to children on apps. “In addition to ensuring that Google stops its illegal and irresponsible behavior to children on YouTube Kids, new policies will be required to address the growing arsenal of powerful digital marketing and targeting practices that are shaping contemporary children’s media culture – on mobile phones, social media, gaming devices, and online video platforms," he said.

In the 1970s, federal regulators created rules to curb the amount of advertising during children's programs. The rules restricted shows from promoting products within their programs and prohibited advertisers from creating entire shows out of their products. On YouTube Kids, dozens of videos are created by  Lego, along with many user-generated videos focused on Lego products.

“YouTube Kids is the most hyper-commercialized media environment for children I have ever seen,” said Dale Kunkel, professor of communication at the University of Arizona. “Many of these advertising tactics are considered illegal on television.”