WASHINGTON – A massive effort by Internet users to prohibit telephone and cable companies from providing better service and prices to preferred customers failed to get through a Senate committee on Wednesday.

After three days of debate, the Senate Commerce, Science and Transportation Committee approved a bill intended to let phone companies and other telecommunications providers better compete in video markets now monopolized by cable companies.

The measure faces an uncertain future because of the controversy over “Net neutrality” – how to ensure that consumers and Internet content providers continue having open and nondiscriminatory access to the Internet.

The committee rejected an amendment by Sens. Olympia Snowe, R-Maine, and Byron Dorgan, D-N.D., that would prohibit phone and cable companies from limiting access to their high-speed Internet networks based on site content or financial arrangements. The vote was 11-11, and ties defeat proposed amendments.

Supporters argued that service providers could give preferential treatment to business partners or use pricing and access limits to discriminate between Web sites and other Internet users.

“What’s at stake is the Internet in the 21st century,” said Snowe, the only Republican to vote for the amendment. “This is the preservation of digital democracy.”

Hundreds of interest groups, ranging from the Christian Coalition to Moveon.org., joined bloggers and the big content providers such as Google Inc. and Amazon seeking protections from Congress against owners of high-speed broadband networks.

Republicans argued against interfering in a system that so far has worked well without government regulation.

Phone and cable companies say Snowe’s and Dorgan’s proposal would stifle investment in broadband technology by restricting what they could charge customers. Both sides have spent millions of dollars on lobbying and advertising on the issue.

The committee chairman, Sen. Ted Stevens, said the legislation would require regulators to preserve the free flow of ideas and information on the Internet by ensuring access to legal content.

Stevens, R-Alaska, also said the House would not accept a measure with the net neutrality language. The House this month passed its version of the legislation after rejecting a net neutrality amendment.

Sen. John Kerry, D-Mass., a supporter of the Snowe proposal, said the bill could face a filibuster in the full Senate if it did not protect users from discrimination.

The chief goal of the wide-ranging bill is to make it easier for phone companies and others to enter video markets now dominated by cable and satellite companies. Supporters hope competition will drive down prices and offer consumers more choice.