The iPhone 4 and 3G-enabled iPad 2 secretly record information about the whereabouts of their users and store that information in unencrypted files, according to two British researchers at the University of Exeter.

Alasdair Allan and Pete Warden levelled the allegations at a conference in Santa Clara, Calif. on Wednesday.

"All iPhones appear to log your location to a file called 'consolidated.db,'" Allan said in a video recording of their presentation, which has already been viewed more than 100,000 times on YouTube. "This contains latitude and longitude coordinated along with a time-stamp. The co-ordinates aren't always exact, but they are pretty detailed."

The discovery happened accidentally while they were investigating which contact information was available on Allan's iPhone 4. What they found is that the device has had recorded his location 220,000 times in the 293 days since he began using it.

"Apple have made it possible for anyone from a jealous spouse to a private investigator to get a detailed picture of your movement," they said.

The tracking function is set in iOS4, Apple's latest iPhone software, as well as on iPads with a cellular data plan. The information about a user's location is also backed up on their computer using iTunes when they synchronize either portable device.

While it doesn't appear that Apple stores the tracking information, "why this data is stored and how Apple intends to use it, or not, are important questions," Allan said.

It would also be relatively easy for hackers to access the unencrypted files, he said, particularly if a user loses their iPad or iPhone.

Apple hasn't commented on the matter.

Meanwhile, Allan and Warden have created a free program that maps the tracking data collected by the devices. And Sam Biddle, an editor at technology website Gizmodo, used the mapping program and published the results online.

"This is a map of everywhere I've been for the last months. Everywhere," he wrote. "I didn't carry around a tracking device. The FBI isn't sending goons in unmarked vans to track me. All I did was use an iPhone."