A digital watchdog and public health group urged US authorities Tuesday to investigate the online marketing practices of alcoholic beverage companies and their impact on young people.

The appeal to the Federal Trade Commission (FTC) and state attorneys general came in a 34-page report issued by the Center for Digital Democracy (CDD) and the Berkeley Media Studies Group of the Public Health Institute.

"The alcohol industry's digital and social media marketing tactics are blurring the boundaries between advertising and content with unprecedented sophistication," CDD executive director Jeff Chester said in a statement.

"The FTC and state attorneys general should launch an investigation into this new threat to young people online."

The report singled out a number of interactive advertising campaigns by beer and liquor companies it said were being used to "promote their products using methods that appeal to youth."

Among the examples cited in the report were a Heineken campaign involving an online virtual community, Smirnoff and Budweiser's use of video sharing website YouTube to promote viral videos and a free iPhone game from Malibu rum.

"Today's young people are living much of their lives online," said Kathryn Montgomery, a professor of communications at American University who co-authored the report, "Alcohol Marketing in the Digital Age."

"With concerns about binge drinking and other dangerous behaviors among underage youth, public health professionals and policy makers must investigate these aggressive new alcohol marketing practices on social networks, mobile phone and other digital media so popular with children and teens."

The report noted that many alcohol companies and websites such as Facebook use age verification filters to try to keep out the underaged, but said the mechanisms were, "at best, imprecise and faulty."

"Age verification efforts don't work," said David Jernigan, associate professor at the John Hopkins Bloomberg School of Public Health. "It doesn't take much imagination for kids to fib about their birthday before entering a website."

In a statement, Lisa Hawkins, vice president of the US-based trade association Distilled Spirits Council, defended the industry's online advertising practices.

"Distilled spirits companies adhere to a rigorous set of content and placement guidelines for advertising and marketing materials in all media, including online and digital communications channels," Hawkins said.

"In today's marketplace, online and digital communications channels are used primarily by adults," she said, "which makes these platforms responsible and appropriate channels for spirits marketers."

"The Distilled Spirits Council proactively engages regularly with social networking sites, other online communications platforms and syndicated demographic data sources to stay ahead of emerging technology," she added.