The study, by website MobilePhoneChecker.co.uk, found most youngsters are now likely to be given cellphones while still in primary school, at an average age of 7-1/2.
A decade ago, the average age was 13.2 years.
A majority of parents in the survey said they give children mobiles for safety reasons and "peace of mind."
Around a fifth of the parents admitted peer pressure was a factor and they bought phones for their children just because so many of their children's schoolmates had them.
"Despite the argument that parents want to keep their children safe at all times, many may think that seven years old is far too young to own a mobile phone," Adam Cable, director of MobilePhoneChecker.co.uk, told The Daily Telegraph.
"However, I have seen four-year-olds who can work their parent's iPhone or iPad perfectly well.
"The protection of children is obviously a key factor in their usage of mobile phones, but as long as the proper precautions are taken to ensure maximum safety of children using handsets, then they absolutely have their benefits," he said.