Just 20% of parents have enforced time limits on their children's smartphone usage.
Some 25% of young UK children now own a smartphone, and almost half of them spend three hours a day glued to the screen.
A recent study by musicMagpie found that parents have become more willing to buy children smartphones at a younger age. A quarter of children under six have a smartphone and just under half of them spend 21 hours a week using it.
One in five UK parents believes that 11 is the "ideal" age to buy a child their first smartphone. The information was sourced when musicMagpie noticed a 300% year-on-year increase of phone purchases for children. More than 2,000 parents were surveyed in the UK.
Samsung was the most popular brand for parents to buy, followed by Apple and Huawei. Children with phones use them mostly for games (38%), followed by music (32%), movies (30%) and Snapchat (23%). More than three quarters of parents spent up to £500 on their child's first phone.
MusicMagpie marketing director Liam Howley said parents should be wary of what their children are doing on smartphones. "The age at which children get their first phones has got even younger, and while many agree that there's no defined age to give a child a phone, there's a lot parents can do to ensure their child's day-to-day life isn't consumed by one," Howley said.
"From restricting the time they spend on the device, to keeping a close eye on what they are downloading, there are many steps parents can go through to limit usage."
Of the 2,000+ parents surveyed, just 20% had put limits on their child's smartphone use per day. About two thirds did not limit how much their child spends on games, music or movies, and 75% did not limit the use of data.
But what is the main reason for buying a child a smartphone? A third of the parents admitted to giving in to their children's pleas, while a fifth conceded it was to keep them entertained.
In the UK, parents spend about £1,000 each year on gadgets for their children.