Apple is set to require iPhone apps to request “explicit approval” before accessing users’ address book details, according to reports.

The news comes following increased attention on app privacy, following the revelation that social networking app Path was uploading full address book content to its servers, in order to detect relationships between users.

This week, VentureBeat said that apps including Facebook, Foodspotting, Foursquare, Gowalla, Twitter, Instagram and Yelp were among those uploading phone book data.

According to Reuters, Apple’s decision comes after two US politicians requested it provides more information on its privacy policies. The company noted that apps which collect user data without permission are “in violation of our guidelines.”

The Register said that Twitter has admitted to storing address book data for 18 months, when a subscriber uses the “find friends” function on an iOS or Android device. The company said that in future it will use the terms “upload your contacts” and “import your contacts,” to give a clearer picture of the process.

VentureBeat detected the extent to which apps uploaded names, email addresses and phone numbers by using a traffic monitoring tool to observe data flowing between devices and the internet.

Although some of the companies denied storing personal data, the transfer of data alone leaves it vulnerable to being intercepted, it was noted. VentureBeat added that although the data could be encrypted during transmission process, the companies often choose not to.

Last week social networking app company Path issued an apology after complaints about the way it handled users’ personal information. The company was found to be uploading data from handset address books to its servers, without explicitly stating that this was the case. Path immediately amended its policy to ask users for permission before uploading their information.