– Google Inc., once boastful that it was the leading defender of a free and open Internet, has gone into the shadows.

Since the Federal Communications Commission proposed in May to let cable and telephone companies offer special Internet fast lanes for companies willing to pay extra, lobbyists for Google haven't visited the agency to intervene, FCC records show. Facebook, the largest social network, also has been absent.

It's a stark change from eight years ago, when Google ran advertisements that called for treating all Web traffic equally, asked its users to contact senators on the issue and dispatched co-founder Sergey Brin to Washington to lobby lawmakers.

"They've definitely faded into the background, and that's very troubling," said Paul Sieminski, general counsel of San Francisco-based Automattic Inc., the publisher of the WordPress blogging platform. "A lot of tech companies look to Google."

An erosion of equality for all Web traffic has the potential to entrench large companies that have staked their turf on the Internet, while making it harder for start-ups to gain an audience. For a company like Google that started in a Northern California garage in 1998 and became the world's largest Internet search provider with $60 billion in revenue last year, there isn't as much incentive to fight.

"Net neutrality got them where they are," said Timothy Wu, a Columbia University law professor in New York City who supports open-Internet rules. "There's a danger that they, having climbed the ladder, might pull it up after them."

Google and Facebook are "quiet and they're not spending much" to ensure that Internet providers treat all Web traffic equally, Wu said.

With Google, Facebook and other technology giants taking a more passive approach, nascent Internet companies and their financial backers are leading the campaign to quash the FCC's proposal and bolster agency authority over Web traffic.

FCC Chairman Tom Wheeler in May won initial approval for rules that could let Internet-service providers such as Comcast, AT&T and Verizon Communications charge more for fast passage over their lines. The ­proposal, which includes prohibitions on blocking traffic, would replace rules voided by a court that said the FCC failed to claim the proper authority.

Google hasn't publicly addressed the rules since the FCC's May 15 vote. In a May 7 letter, Google and more than 140 software, social-media and technology companies said Wheeler's fast-lane proposal would be "a grave threat to the Internet."