Around 970,000 children are regulars on the site, and have made it an integral part of their daily lives, The Sun newspaper reported.
At least 46 percent say they use the site occasionally.The report by analysts Mintel shows everyday usage of Facebook is most common among girls aged 10 to 12 -- with 54 percent of them logging in.
The next most popular social networks are Twitter and Club Penguin, but the frequency of visits is much lower, with less than 10 percent of children using them.
Experts say peer pressure is the "key motivation" for using a particular social network.
Nearly two-thirds of seven to 12-year-olds use a social networking website because their friends do.
"Today's children are well versed in all aspects of the internet, with almost a million children aged seven to 12 using Facebook -- highlighting just how popular the site has become," Ina Mitskavets, author of the "Children's Lifestyles" report from Mintel, was quoted as saying.
The research also revealed children spend approximately three hours and five minutes a day -- both on school days and weekends -- watching TV.