WASHINGTON (Reuters) - A senior U.S. lawmaker plans to introduce a bill in January that would bar Internet providers like AT&T Inc from blocking Web content, setting up a renewed battle over so-called network neutrality.

Democratic Senators Harry Reid (R) and Byron Dorgan talk in Bogota November 28, 2007. REUTERS/Daniel Munoz

Sen. Byron Dorgan, a North Dakota Democrat, believes a law is essential to prevent telephone and cable companies from discriminating against Internet content, even though regulators have taken actions to enforce free Web principles, a top Dorgan aide said on Thursday.

“We feel that legislation is definitely necessary,” said Frannie Wellings, telecom counsel to Dorgan, speaking at a University of Nebraska law school event on changes in telecom law after the election of Democrat Barack Obama.

Dorgan has been influential on the issue, and will be among the highest ranking Democrats on the Senate’s Commerce Committee when it reconvenes in January.

The net neutrality fight pits Internet service providers (ISPs) like AT&T against content companies like Google Inc and Microsoft Corp.

The ISPs, which also include Verizon Communications Inc. and cable company Comcast Corp, say they need to manage the ever-growing traffic on their networks without government interference.

Content companies say the ISPs hold too power much to block or slow down traffic requiring more bandwidth, such as movie downloads, or certain content altogether.

President-elect Barack Obama supports net neutrality legislation. The election of Obama and more Democrats who back the concept adds momentum to the cause, Wellings said.

A recent Federal Communications Commission decision ordering Comcast to stop impeding the sharing of certain content between users proves regulators already have the authority, an AT&T official said.

“The current (FCC) principles already deal with unreasonable discrimination,” said Jim Cicconi, AT&T executive vice president for regulatory affairs, pointing to the Comcast case.

The public would not pay for its Internet services if AT&T discriminated against content, he added. “We’d be shooting ourselves in the foot.”

Comcast is suing the FCC over the issue, and much depends on the outcome of that case, experts said. If the court sides with Comcast, legislation will become much more likely.

“The telephone and cable companies say trust them,” said Markham Erickson, director of the Open Internet Coalition, a trade group that lobbies for net neutrality, with members such as Google and eBay Inc. “We will trust but verify.”