Ofcom: Almost a quarter of kids aged 5-7 have smartphones
Social media use also rose in the age group over last year with nearly two in five using messaging service WhatsApp, despite its minimum age of 13.
In its annual study of children's relationship with the media and online worlds, Ofcom said the percentage of children aged between five and seven who used messaging services had risen from 59% to 65%.
The number on social media went up from 30% to 38%, while for livestreams it increased from 39% to 50%. Just over 40% are reported to be gaming online - up from 34% the year before.
Over half of children under 13 used social media, contrary to most of the big platforms' rules, and many admitted to lying to gain access to new apps and services.
"I think this is a wake up call for industry. They have to take account of the users they have, not the users that their terms and conditions say they have," Mark Bunting, from Ofcom's Online Safety Group told BBC News.
"We've known for a long time that children, under the age limit on a lot of the most popular apps, are widely using those apps, and companies are now under a legal obligation to take steps to keep those children safe," he added.
