The latest flare-up comes after Apple made changes to its new mobile operating system that it advertised as improving privacy, but that also give the company an edge over other app makers in using the location-tracking features of the device.

In his first comments on the matter, the top Democrat in charge of a sprawling antitrust investigation into Silicon Valley juggernauts cites the change as one of a number of factors his committee will be exploring as part of an antitrust probe.

"I'm increasingly concerned about the use of privacy as a shield for anti-competitive conduct," said Rep. David Cicilline of Rhode Island, chairman of the House Judiciary antitrust subcommittee.