YouTube has accused T-Mobile (TMUS) with intentionally throttling its video traffic. A company spokesperson said in a statement to Fortune on Wednesday that while T-Mobile’s attempts at “reducing data charges can be good for users,” the practice does not “justify throttling all video services, especially without explicit user consent.”

At the core of YouTube’s argument is Binge On, a program T-Mobile unveiled last month. Binge On allows T-Mobile customers to watch videos from 24 different services, including Netflix (NFLX), Hulu, and HBO Go, without eating into their data limits. While T-Mobile CEO John Legere touted the move as a game-changer in the mobile industry, there are some caveats. For one, video is streamed at DVD quality with 480p resolution. Since many devices come with higher-resolution displays, it was somewhat disappointing to those who desire better-quality visuals. For T-Mobile, it’s a way to downgrade video quality to save on data consumption.

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At launch, YouTube was not included in the Binge On list, and is still not part of that program. However, YouTube argues that T-Mobile has placed the same data-throttling limits on its high-definition videos. What’s worse, the company argues, T-Mobile is allegedly doing so without getting customer consent.

T-Mobile has acknowledged that through the Binge On program, “almost all other video streaming is optimized for mobile.” In other words, the company is downgrading video quality even on the services that aren’t part of its free program. T-Mobile says the move allows customers to “watch three times more video” with their data plans. Only the 24 companies that have met T-Mobile’s “technical criteria” won’t use up data.

A T-Mobile spokesman pointed to a tweet from Legere on Tuesday. Oddly, the tweet, which the T-Mobile spokesman called a response, did not mention YouTube’s charges, and only touted the Binge On program.

“Our customers [love] Binge On, streaming video without hitting their data bucket and complete control to turn it on/off at will,” Legere tweeted. Indeed, T-Mobile explicitly says on its website that video-quality downgrading can be turned off at any time, allowing users to resume higher-quality access.

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That has done little to quell unrest over the Binge On program. The Internet Association, an organization that acts on behalf of Internet companies to push public policy, issued a statement on Tuesday, saying that “T-Mobile’s new ‘streaming optimization’ program appears to involve throttling of all video traffic, across all data plans, regardless of network congestion.” Google is one of The Internet Association’s member companies.

“Reducing data charges for entire classes of applications can be legitimate and benefit consumers, so long as clear notice and choice is provided to service providers and consumers,” the organization said in its statement. “However, a reasonably designed zero-rating program does not include the throttling of traffic for services or consumers that do not participate.”

The Binge On program has also caught the Federal Communications Commission’s eye. In a letter to T-Mobile dated Dec. 16, the FCC requested more information on the program to determine whether T-Mobile is treating all services fairly.

WATCH: For more on T-Mobile’s Binge On program, check out the following Fortune video:

“As you may be aware, concerns have been expressed about the Binge On program,” the letter reads. “For example, some have argued that the technical requirements of the Binge On program may harm innovation by making certain video apps more attractive than others. Others have asserted that the reduction of video quality has harmed some users.”

The inquiry is part of a broader concern over net neutrality. While the topic has been debated for years, in February, the FCC adopted rules that require Internet Service Providers, including cellular networks, to treat all traffic fairly and not discriminate against certain services. Those rules also ban selectively throttling traffic on certain types of applications, including video.

In its letter to T-Mobile, the FCC acknowledged that T-Mobile believes “that Binge On is not a network neutrality problem,” and last month, FCC chairman Tom Wheeler told a reporter that Binge On does not violate any net neutrality rules.

“It’s clear in the Open Internet Order that we said we are pro-competition and pro-innovation,” Wheeler said. “Clearly this meets both of those criteria. It’s highly innovative and highly competitive.”

T-Mobile has been asked to respond to the FCC by Jan. 15. In its statement, The Internet Association said that it “applauds the FCC for seeking information on this practice and its potential harm on consumers and online applications and services.”