It's a recommendation in a report released by researchers from the Polytechnic University of Valencia that also suggests content classifications for mobile phone usage by age, such as is done for video games.
"Verification of age upon access to mobile phone services is not effective because the child can also falsify their age by checking a different box," researcher Maria de Miguel Molina said.
"However, operators could be made aware of the age of their young users if their parents were to disclose such information when purchasing a mobile phone for their child," she said.
"This information could then be registered," said de Miguel, who headed the study on mobile services aimed at children in Spain.
"Up until now we thought we could control youngsters' access to the Internet on the household desktop by locating it in a visible place, for example, and ensuring that children use the Internet properly," she said.
"But smartphones have opened up new doors."