Pete Warden and Alasdair Allan said the tracking facility was added in iOS 4 and stored detailed co-ordinates of exact locations visited by handset owners, sparking serious privacy concerns.
"Apple has made it possible for almost anybody – a jealous spouse, a private detective – with access to your phone or computer to get detailed information about where you've been," Warden told the Guardian.
The researchers found that a file within iOS contained longitude and latitude co-ordinates alongside a time stamp - and that combining these details with a simple mapping application would give anyone a detailed breakdown of everywhere a user had been.
The researchers said they had looked for similarly intrusive tracking technology in Android and had not found any evidence, but stressed they did not believe the data was being beamed back to Apple.
Mobile networks already store location information, but that is only available to law enforcement officials with a search warrant. Apple also faces criticism from privacy watchdogs because the tracking data is collected without user consent.
According to the researchers, the data would be transferred to new handsets if the consumer upgraded, but the question remains why Apple would even want to store the data.
"Apple might have new features in mind that require a history of your location, but that's our speculation,” the Guardian quoted the researchers as saying.
“The fact that [the file] is transferred across when you migrate is evidence that the data-gathering isn't accidental."
Apple has not yet responded to a request asking why it was collecting the data.