"[The briefing] doesn't surprise me at all and I think it is consistent with other research about TV watching and the effects on children," she said.
"These things are quite well known, that sedentary children who are not out exercising, not out mixing socially, are more likely to have problems, less likely to have concentration spans that allow them to succeed at school and less likely to have exposure to both successes and failures that life throws up and develop a more resilient temperament as a result."
Socialising and being active were important to a child's development, so the more TV they watched, the less time they spent developing those important faculties, she said.
"Children who spend lots of time sitting watching TV or in front of other electronic media are not allowing themselves to get out and test themselves against the world and being with peers and the social opportunities that that creates.
"They are possibly less likely to be involved in sports and other activities where children have the opportunity to develop their self-esteem and do something purposeful."
The content of some TV programmes children were exposed to was also an area of concern, she said.
"Another dimension is that they are viewing a world on TV that portrays a certain life and they may be trying to measure up to that and see if they fit in with the brave and the beautiful which we see on TV."
There were positive educational games and TV programmes, but parents needed to put some limits on the amount of time their kids spent in front of the screen, she said.
The British study was based on research done by the Children's Society among 42,000 youngsters aged 8 to 15, and on other data.
- additional reporting Independent