The number of 12 to 14-yearold children who own a mobile phone has more than doubled in six months, prompting concern among parents' groups.
A survey by a consulting firm, Amarach, has found 120,000 children between the age of 12 and 14 own a mobile, a rise of almost 70,000 since last August.
A further 30,000 children within this age group regularly use mobile phones which belong to parents, friends or relatives.
Mr Michael O'Regan, president of the National Parents' Council Association for Vocational Schools and Community Colleges, described the figures as "frightening".
"There are concerns over health risks, and no one has yet clarified how mobiles affect people," he said.
"Many parents have contacted me about bullying over text messages."
The Amarch survey, conducted during January and February, found 77 per cent of girls and 71 per cent of boys aged between 12 and 14 use mobile phones.
Many of the young people surveyed view the mobile phone as a fashion accessory, although most use it to send more than 20 text messages a week.
Mobile use among 15 to 24year-olds is even greater, with 94 per cent of females and 79 per cent of males owning a handset.
This is equivalent to almost 570,000 users, up from 415,000 since last August.
According to the survey, the average monthly expenditure by 15 to 24-year-olds is £33.
Ms Fionnula Kilfeather, chief executive of the National Parents' Council Primary, said yesterday children as young as six were using mobiles.
Young children faced considerable advertising pressure to purchase them, she added.
Eircell recently introduced a product aimed at younger users called the "Buddy Phone". This has a limited dialing facility which can be pre-programmed by parents.
However, an Eircell spokeswoman denied the company was actively targeting 12-14-year-olds with its prepaid product through its advertising.
Amarach conducted interviews with 300 children aged between 12 and 14 and 300 people aged between 15 and 24 for the survey.