The average child is given a handset at the age of 11 but nearly one in 10 has a phone at less than half this age.
Parents spend an average £125 on their youngster's gadgets - and around £246 on their own mobiles, the study found.
Children spend an average £11 per month on their mobiles - less than parents who spend £19, the survey revealed. But more than one in 10 (11%) youngsters spends more than their mother or father.
The study, by comparison site uSwitch.com, found children were, on average, given their first mobiles soon after starting secondary school at 11 years and eight months.