During a period of one year, the regulator reported a 300% rise in complaints from consumers unexpectedly receiving expensive phone bills.
UK premium rate phone service regulator, PhonepayPlus, has warned parents over children running up phone bills due to purchases made for mobile apps and accessing social media sites.
The regulator said that in one year, complaints about phone bills rose by 300%.
The report suggests about 63% of 11 to 16-year-olds have downloaded a free app on their smartphones which later found to have hidden costs the children are not aware of.
PhonepayPlus warns that some free apps contain malware that tricks smartphone users into running up their phone bill.
PhonepayPlus said that social media platforms have been benefitting from children's ignorance and were causing concern among parents.
The regulator said that children between 12 and 14 years were tricked into sharing and liking a promotion on Facebook for supermarket vouchers.
The agency advised parents to register phone's as a child's phone with the mobile network, which give them control, including pay-as-you-go or blocking certain services.
PhonepayPlus also urged parents to be familiar with apps downloaded by children and about their costs, along with the price of upgrades.
PhonepayPlus chief executive Paul Whiteing said that connected devices will define the age in which today's children live and the agency is determined to ensure that they can receive the benefits while being protected from the risks.
"Smartphones in children's pockets can burn holes in parent's wallets, so we are working with partners across industry and other agencies to prevent this," Whiteing said.
"This is a real challenge for parents and for us as a regulator but this plan meets that challenge head on."