Eight out of 10 Web sites selling mobile phone ring tones and graphics are tricking people with hidden fees or false advertising, the EU’s consumer affairs commissioner said Thursday.

The commissioner, Meglena Kuneva, said a Europe-wide investigation found shoddy sales practices such as hiding the true cost of downloads or not telling customers they are signing up for a subscription.

“It’s clear that consumers have been ripped off,” she said.

She said she is telling national governments to go after crooked traders.

Ring tones _ usually aimed at teenagers _ make up almost a third of mobile content in Europe, racking up 691 million euros ($1.1 billion) in sales last year, the EU said.

The European Commission checked some 500 Web sites, finding that 80 percent broke consumer advertising rules. It took action after receiving complaints from shoppers unhappy at being forced into subscriptions or extra charges.

“To be safe buying these services, check the fine print every time and make sure you are not signing up for more than you bargained for,” Kuneva warned.