WASHINGTON (Reuters) - Technology companies including Alphabet Inc GOOGL.O and Facebook Inc FB.O on Thursday threw their weight behind a congressional bid to reverse the Trump administration’s plan to repeal Obama-era rules designed to protect an open internet.

FILE PHOTO - Supporters of Net Neutrality protest the FCC's recent decision to repeal the program in Los Angeles, California, November 28, 2017. REUTERS/ Kyle Grillot

U.S. Senate Democrats said last month they had the backing of 50 members of the 100-person chamber for a reversal of the Federal Communications Commission’s (FCC) plan, leaving them just one vote short of a majority.

The FCC voted along party lines in December to repeal net neutrality regulations. Those rules, introduced in 2015, were lauded by tech companies and consumer groups but denounced by internet service providers as hindering investment.

The Internet Association, which represents Google's parent, Facebook, Amazon.com Inc AMZN.O, Microsoft Corp MSFT.O, Netflix Inc NFLX.O and many others, said in a letter on Thursday to Senate leaders that it backed the Senate effort to reverse the vote, but also called for a long-term fix.

“The internet industry urges Congress to legislate a permanent solution,” the group said in the letter made public on Thursday. “The time has come for a bipartisan effort to establish permanent net neutrality rules.”

A public backlash against the FCC’s plan, especially among younger people, has raised concerns among some politicians about how the issue might play out in the 2018 congressional elections.

More than 20 U.S. state attorneys general are also mounting a legal challenge of the FCC’s vote to reverse the rules introduced in 2015 that prevent internet providers, such as AT&T Inc T.N and Comcast Corp CMCSA.O, from obstructing information they transmit to customers or offering paid fast lanes, also known as paid prioritization.

While the FCC reversal will lift those restrictions on providers, a future FCC could reimpose them and internet providers have also urged Congress to write new laws to end a decade-long dispute over the future of the internet. Democrats have shown little interest in working to write new rules.

Internet companies say that without net neutrality protection, many Americans will have little recourse. The letter on Thursday said that “more than half of all Americans have no choice in their provider, and 87 percent of rural Americans have no choice.”

USTelecom, which represents AT&T, Verizon Communications Inc VZ.N and other phone companies, said "we couldn’t agree more that Congress needs to engage on (net neutrality) to craft a bill that addresses the key issues, includes all players in the ecosystem and finally resolves the disruptive policy back and forth."