Facebook Inc. is moving forward with plans to make users’ addresses and mobile phone numbers available to apps that people use on the site, however this would require explicit permission from users. This feature had already prompted privacy questions from U.S. lawmakers.

The company reiterated its plan to go ahead with opening up users’ personal details, which was first revealed in a blogpost on its Developer blog in January — opaquely entitled “Platform Updates: New User Object fields, Edge.remove Event and More” — but suspended three days later in the face of angry responses from privacy advocates.

Markey, a Democrat from Massachusetts, and Barton, a Republican from Texas, sent a letter Feb. 2 to Facebook Chief Executive Officer Mark Zuckerberg asking about the company’s plans for the feature.

The social-networking site has not determined when it will reintroduce the feature but is evaluating ways to “enhance user control,” including “potential additions to the permissions screen,” Marne Levine, Facebook vice president of global public policy, wrote in a Feb. 23 letter to U.S. representatives Edward Markey and Joe Barton.

Facebook also is “actively considering” whether to allow applications to request contact information from minors, Levine said in the letter.

“Mobile phone numbers and personal addresses, particularly those that can identify teenagers using Facebook, require special protection,” Markey said in a statement today.

“I’m pleased that Facebook’s response indicated that it’s looking to enhance its process for highlighting for users when they are being asked for permission to share their contact information,” he said.

Andrew Noyes, a Washington-based spokesman for Facebook, said the company’s letter speaks for itself and had no additional comment. Facebook is meanwhile experimenting with a new “privacy-policy” that would be more like a guide to how personal information is used, rather than a long legal document.