Parents have been warned to "regain control" of their own households in the face of a growing tendency of children to sit for hours every day in front of computers and the TV.
Psychologist Dr Aric Sigman said a generation of children is developing a lifelong habit and in some cases dependency on small screens because of over-exposure in childhood.
Average screen time for young British adolescents is now at 6.1 hours a day and rising with 10 to 11-year-olds having access to an average of five screens at home, he will tell a scientific session of the Royal College of Paediatrics and Child Health (RCPCH) annual conference.
By the age of seven years old a child born today will have spent one full year of 24 hour days watching screen media, he will tell the conference in Glasgow.
Dr Sigman said even average levels of daily screen viewing were now strongly associated with a significantly increased risk of type 2 diabetes and cardiovascular disease.
He added that there were concerns that extensive computer game playing in children may lead to long-term changes in the brain's circuitry that resemble the effects of substance dependence.
"Technology should be a tool, not a burden or a health risk," he said.
"Whether children or adults are formally 'addicted' to screen technology or not, many of them overuse technology and have developed an unhealthy dependency on it.
"While there are obviously a variety of different factors which may contribute to the development of a dependency - whether it involves substances or activities - the age, frequency, amount of exposure along with the ease of access and the effects of role modelling and social learning, all strongly increase the risk.
"All of these contribute to a total daily exposure to, or 'consumption of', an activity.
"And all are prerequisite factors that contribute to the risk of dependent overuse of technology."
Dr Sigman said parents should not fall into the trap of "passive parenting" in the face of the problem.
He said rules and limits should be enforced on screen time for children. He added that the age of first exposure to the small screen should be raised to at least three years old.
Parents who constantly check and use smartphones and iPads in the presence of their children may be adding to their children's overuse of the small screen, he said.
