Technology companies have been criticised after certain third-party applications on their platforms failed to provide clear enough indications to users over how their personal data will be used and stored.
Google recently came under fire over claims that it circumvented security in Safari browsers in iPhones to track millions of users of its services, while Apple was criticised for allowing the Path social network to store the address books of thousands of iPhone users.
California's attorney general said yesterday that the new rules mean that six major tech firms - Amazon, Apple, Google, Microsoft, BlackBerry-maker Research in Motion (RIM) and Hewlett-Packard - and developers on their platforms must offer privacy policies that users can fully understand before downloading apps.
Technically, the ruling only applies to California, but it is widely expected to set the trend for privacy policies on the global apps marketplace, including Google Android, Apple iOS, Microsoft Windows Phone and RIM's BlackBerry.
California Attorney General Kamala Harris said that it had previously been unclear to app developers whether US online privacy protection law applied to mobile apps, but the ruling is intended to resolve that confusion.
Harris said that developers should be aware that authorities are prepared to enforce the newly clarified California Online Privacy Protection Act against any cases of infringement.
"We take a great deal of pride in the technology that was born in our backyard," Harris said. "There's no desire on any of our parts to slow down what's potentially life-changing and world-changing technology. But we also shouldn't have to accept false choices between privacy and access to innovation."
The new system will not actually limit the data that apps can 'grab' from smartphone users, including email addresses, location, and personal contacts, but it will require the services to inform customers of what is being taken.
The six participating companies will meet the attorney general in six months to assess compliance among their developers, although Harris acknowledged that there was no specific timeline for enforcement.