T-Mobile's controversial "Binge On" program has added an industry heavyweight to its streaming video service lineup.

Google said in a blog post that YouTube and Google Play Movies have joined the program.

Binge On launched back in November with 24 services, such as Netflix (NFLX) and HBO Go. The service lets users stream video without it counting toward a customer's data plan.

Google (GOOG), however, agreed to join Binge On only after T-Mobile (TMUS) made changes to the service.

"The initial implementation of the Binge On program raised questions from both users and video services, including YouTube," Google said.

T-Mobile, it said, has now agreed to give customers "more help to understand" how the program works and allowed Google to retain more control over how its steaming content is "optimized."

"We think these changes, which T-Mobile is making for all users and video providers on a non-preferential basis, can help insure the program works well for all users and the entire video ecosystem," Google said.

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The Binge On program was initially met with criticism, with several reports and opinion pieces accusing T-Mobile of "throttling" customers by downgrading video quality.

T-Mobile CEO John Legere said at the time that special interest groups were purposely confusing people about the program.

"Throttling is slowing data and removing customer control," Legere said. "Let me be clear: Binge On is neither of those things ... I think they may be using net neutrality as a platform to get into the news."

-- Hope King contributed to this report.