WASHINGTON, Aug 8 (Reuters) - The head of the U.S. communications regulator on Friday said he is asking all large U.S. wireless carriers to explain how they decide when to slow down download speeds for some customers, after questioning Verizon Wireless about such a plan.
Verizon, the No. 1 wireless carrier, in July said the top 5 percent of high-speed data users on its older, unlimited data plans might experience slower speeds starting Oct. 1.
Federal Communications Commission Chairman Tom Wheeler wrote to Verizon that he was "deeply troubled" by the plan, concerned that the company's decision to slow down, or "throttle," data was based on consumers' data plans instead of network or technology needs.
Verizon defended the practice, telling Wheeler it was a narrow, "widely accepted" and lawful way to manage networks.
But Wheeler on Friday indicated he was not convinced.
"'All the kids do it' was never something that worked for me when I was growing up," he told reporters after the monthly FCC public meeting.
"My concern in this instance - and it's not just with Verizon, by the way, we've written to all the carriers - is that it is moving from a technology and engineering issue to the business issues ... such as choosing between different subscribers based on your economic relationship with them."
The FCC did not disclose the letters to the other big carriers, AT&T Inc, Sprint Corp and T-Mobile US . But an FCC official said Wheeler asked other carriers questions similar to those asked of Verizon about their network management policies and practices.
Verizon was the first to receive such a letter because it was the only one with a new announcement of a policy change, the official said, and letters to other carriers followed Verizon's response.
Representatives for AT&T, Sprint and T-Mobile did not immediately respond to requests for comment.
(Reporting by Alina Selyukh and Marina Lopes; Editing by Leslie Adler)