– Which? executive director Richard Lloyd
It's far too easy for children to run up huge bills on phone apps when most default settings allow 'in-app purchases' without asking for a confirmation or password.
Parents who want to stop this should either turn off the default setting or switch on parental controls so that passwords are required for any in-app purchases.
If your child has run up a huge bill without your knowledge, contact the app store or manufacturer as you may be eligible for a refund.
"Free" web and app-based games aimed at children are being investigated by the Office of Fair Trading over concerns about costs for extras. In March, a five-year-old boy racked up charges of £1,700 playing games on his parents' iPad.