Emma Draper, of the Privacy International campaign group, said: 'Your personal information is a precious commodity, and companies will go to great lengths to get their hands on as much of it as possible.'
The Facebook app has been downloaded to Google's Android smartphones more than 100million times, yet few of its users are thought to know that they have agreed to give Facebook the right 'to read SMS messages stored on your device or Sim card'. Apps are also used to identify the location of users through global positioning software and access the phone numbers and email addresses of their contacts.
They can also be used to gain information about the app users' web browsing history.
These details are often sold on to advertisers and market research companies, exposing those downloading the apps to unwanted advertising and spam messages.
Daniel Rosenfield, director of app company Sun Products, said selling on the information was far more lucrative than charging for the app. He said: 'The revenue you get from selling your apps doesn't touch the revenue you get from giving your apps away for free and just loading them with advertisements.'
Chris Brauer, of the centre for Creative and Social Technology at Goldsmiths, University of London, said: 'Most adults have smartphones now. They are a source for incredibly rich information about people's lives. A lot of apps are fronts for various companies who are now capturing this data.'
A spokesman for Facebook said the request for permission to read text messages was to allow the app to read and write data between itself and the phone's SMS feature, rather than for the company to trawl individuals' messages.
He added: 'If Facebook ultimately launches any feature that makes use of these permissions, we will ensure that this is accompanied by appropriate guidance.'
Google said: 'From the beginning, Android has had an industry-leading permissions system which informs consumers what data an app can access and requires users' approval before installation.'
Flickr and Yahoo! did not respond to calls from the Mail.
- DAILY MAIL