Tom Wheeler, chairman of the US Federal Communications Commission (FCC), said he was “deeply troubled” by Verizon Wireless’ proposal to slow 4G data speeds for certain users when there is a high demand.

The US operator argued its move should be seen as network management because it will only reduce data speeds if users are causing congestion.

But in his open letter to Daniel Mead, the US operator’s chairman and CEO, Wheeler wrote: “Reasonable network management concerns the technical management of your network; it is not a loophole designed to enhance your revenue streams. It is disturbing to me that Verizon Wireless would base its network management on distinctions among its customers’ data plans, rather than on network architecture or technology.”

The operator’s plan applies to the top five per cent of 4G data users on unlimited data plans when they are connected to cell sites with high demand.

In a statement, Verizon Wireless said: “What we announced last week was a highly targeted and very limited network optimisation effort, only targeting cell sites experiencing high demand.”

Wheeler’s letter follows the FCC’s proposal on net neutrality and seems to indicate the chairman wants to establish the commission’s credentials in this area.

He also posed three questions to Mead: What is your rationale for treating subscribers differently on the basis of their tariff, rather than network architecture or technological factors? Why is Verizon Wireless extending speed reductions from 3G to its supposedly more efficient 4G network? And how can the operator justify the move given its current regulatory obligations?