The Federal Communications Commission spent years trying to impose rules on broadband providers like Verizon Communications (VZ) and Comcast (CMCSA) to prevent them from throttling, blocking or otherwise discriminating against some web sites. But the Internet service providers kept suing the FCC and getting net neutrality rules thrown out.

So last year, the FCC changed its approach, opting for a more legally defensible basis for its rules by classifying broadband Internet service as a classic telecommunications service under the law. And classic telecommunications service has always been one of the most highly regulated industries in the country. At the same time, the agency promised it wouldn’t impose most of that regulatory burden–including price controls and mandatory contributions to the universal service fund–on Internet companies.

But privacy was another matter. Telephone companies are subject to strict limits on what they can do with data about customers’ calling habits, and the FCC said it planned to look at similar rules for Internet service now.

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The effort, which has been slammed by the industry, picked up some additional momentum on Monday, when six Democratic senators including former presidential hopeful Bernie Sanders released a letter to the FCC seeking new privacy rules.

“In 2016, broadband access is no longer a luxury, it is now as essential as phone service,” the group, which also included Massachusetts Sen. Elizabeth Warren and Vermont Sen. Patrick Leahy, wrote. “Like the phone companies of the twentieth century, internet service providers are gatekeepers that control the infrastructure that Americans depend on to access vital applications and services.”

Protected information should include Internet usage, online activities, and service payments, the senators said. And Internet service providers should be required to get affirmative consent from customers before sharing the information with affiliated companies or third parties.

Customers should not be charged more to protect the privacy of their information, as some companies have sought, the senators urged. “Not only is a pay-for-privacy standard counter to our nation’s core principle that all Americans have a fundamental right to privacy, but it also may disproportionately harm low-income consumers, the elderly, and other vulnerable populations,” the group wrote.

The service providers have said that new rules are unneeded and protested that Internet sites such as Google (GOOGL) collect just as much or more information and wouldn’t be subject to any FCC restrictions.

The FCC announced its proposed rules on March 31 and asked for public comment. The agency typically would come back with final rules in six to 12 months.