T-Mobile deal 'may breach US net neutrality' rules
T-Mobile's new "unlimited" data plan may breach US net neutrality rules, campaigners have said.
The firm claims it offers "unlimited access to the mobile internet", but it charges extra for some services.
The digital rights group the Electronic Frontier Foundation told the news website the Daily Dot it thought that would contravene the rules.
US authorities barred internet service providers from blocking access or speeding it up for a fee.
Jeremy Gillula, the senior technologist at the foundation (EFF), told the Daily Dot that, while the organisation was still in the process of gathering information, "from what we've read thus far it seems like T-Mobile's new plan to charge its customers extra to not throttle video runs directly afoul of the principle of net neutrality".
On Thursday, T-Mobile announced it was to start offering "unlimited everything - talk, text and high-speed smartphone data" for a single price, rather than a deal that provides a finite amount of data per month.
The firm said the $70 (£53) per month deal, which is named T-Mobile One, was a "radically simple subscription to the mobile Internet. One low price. Unlimited everything. That's it. It doesn't get any simpler than that".
But it only includes standard definition video and customers wanting high definition need to pay $25 (£19) a month extra.
And T-Mobile added that people who use large quantities of data will be placed at a disadvantage compared to those who use less than 26 gigabytes per month and "may notice relatively slower speeds but only at specific times and places that may experience high, competing network demand or congestion".
It said only three per cent of users were likely to be affected.
According to Mr Gillula, limiting video to standard definition unless a premium is paid risks breaching the US Federal Communications Commission's Open Internet Order, which "explicitly said that ISPs can't throttle traffic based on its type, or charge customers more in order to avoid discriminatory throttling".
T-Mobile did not respond to a request for comment.
US net neutrality rules instituted last year were designed to protect the open internet. They mean that broadband cannot slow down users' connections unless the customer pays more. Nor can the firms strike deals with content companies to prioritise delivery of their material.
Matthew Howett, an analyst at Ovum, told the BBC that net neutrality rules in both the US and EU were "new and generally untested" and firms were still "getting to grips with what is acceptable and what isn't".
He said: "Critically in the US, carriers believe the FCC overstepped the mark by imposing the rules and are likely to be more hostile to them if they are challenged in court.
"Ultimately, a balance needs to be struck between protecting the consumers on one hand and allowing for innovation and investment in networks on the other.
"To some extent, rule makers will be relying on competitive pressures between carriers and the prospect of consumers voting with their feet if they don't like what's on offer."
In January, T-Mobile was accused of breaking net neutrality rules with its video streaming service Binge On. It included unlimited amounts of low-resolution video with partnered firms. But it was claimed that the deal also affected the quality of other providers' videos, even if they were not a partner.
T-Mobile's chief executive John Legere posted an expletive-filled response on Twitter; for which he later apologised.