Edge providers and public activist groups got together on a letter Tuesday (May 24) calling on the FCC to bring its investigation of zero-rating plans out into the open.

Last fall, FCC chairman Tom Wheeler announced that the agency had begun investigating the zero-rating plans of T-Mobile, Comcast, Verizon and AT&T under its Open Internet general conduct standard, but the groups want the FCC to open a formal proceeding with a chance for outside input from stakeholders.

"In the Open Internet Order, the FCC declined to issue a bright-line rule against zero-rating, noting a lack of consensus on the issue in the record," they wrote in a letter to Wheeler. "However, in the time since the Order was released, ISPs have created a broad enough set of test cases that a decision on each of them would have much the same effect as a new rule, only without the same public participation and transparency.

"Making decisions on these cases would set precedents for future practices, and would have implications for the Internet ecosystem that reach far beyond the stakeholders directly affected by these individual plans," they added. "These decisions are too important to happen behind closed doors."

They cited the very public nature of the Open Internet rule process that generated the general conduct standard now being applied, and said the zero-rating issue should get similar wide and deep participation.

"The FCC’s process in this critical area would be immeasurably enriched by the participation of diverse stakeholders, many of whose input helped shape the Open Internet rules," they said. "Together, we stand ready to contribute to your careful evaluation of this important issue, to protect an open Internet where innovation, competition and civil rights can thrive."

Among those standing ready were Mozilla, Kickstarter, Pinterest, Vimeo, Etsy and Yelp, as well as Common Cause, Fight for the Future and the Future of Music Coalition.