A survey of 2,000 youngsters found that two out of three spend an average of two hours a day on social media, and more during school holidays.
A similar number admitted they had sent a text to a member of their family while sitting in the same house.
Travel rewards firm Avios said its study found that family time was more likely to consist of watching TV than eating a meal together at the table.
Psychologist Dr Aric Sigman said: “These results indicate that children are clearly spending more of their spare time in the virtual world, reinforcing the need for families to take stock and ensure children spend more time in the real world.”
Three out of four teenagers said they could not last a day without using social media, with one in seven admitting they would not last an hour.