The request is the latest development in a controversy over whether iOS apps need to ask for an iPhone owner's consent before gathering contact information from the phone. The issue arose after reports that the social-networking app Path was accessing and collecting iPhone users' address book data without seeking their consent.

Rep. Henry Waxman, ranking member of the committee, and Rep. G.K. Butterfield, ranking member of the Subcommittee on Commerce, Manufacturing and Trade, wrote to Apple CEO Tim Cook on Feb. 15, citing the Path issue and asking nine questions about Apple's iOS app developer policies regarding privacy.

Apple responded on March 2 with a letter that outlined its iOS app review guidelines, noting that the rules said apps could not transmit data about a user without obtaining prior permission and informing them how and where the data would be used. It said "the vast majority" of the 550,000 apps from third parties don't collect or transmit any user data. The company has also announced that a future software release will include a mechanism for explicit user consent to access address-book data, similar to the current consent process for location data.

On Wednesday, Waxman and Butterfield wrote back to Cook and said the March 2 letter didn't answer all of their questions. They also raised new questions about reports that apps can access photos on Apple mobile devices.

"To help us understand these issues, we request that you make available representatives to brief our staff on the Energy and Commerce Committee," Waxman and Butterfield wrote. Waxman, of California, and Butterfield, of North Carolina, are both Democrats.