An expert has said that he has serious concerns over how children could use personal location tracking services like Google Latitude.

John Carr, secretary of the UK's Children Charity Coalition for Internet Safety, said that the web body had issues with Google Latitude and personal data, and the way consent is obtained to use it.

Latitude was released by Google in February, and lets users show selected friends their location using their mobile phone.

"Imagine you're on Facebook or Twitter with your personal profile, and you hook in Latitude or Fire Eagle, or one of these geo-location services," Carr said.

"You've got 5,000 friends? You haven't got 5,000 friends, you've got 5,000 people who now know exactly where you are, in real-time, 24/7, 365 days of the year."

He said that if an adult who knew what they were getting into chose to do that, it was their own business.

However, he said that many children didn't have the capacity to know about the risks that they were undertaking by using these services.

He went on: "And yet, because these are free and paid for by advertisers, that's already happening and is happening more. It will raise all sorts of issues."