In a blow to the cable TV and telephone industries, Senate Commerce Committee Chairman Ted Stevens told reporters last week that he believes in the need for network neutrality among broadband Internet access providers.

But Sen. Stevens, R-Alaska, said he wasn’t sure how to define a neutrality principle that industry critics believe is vital to prevent cable TV and phone companies from using their control of new broadband networks to discriminate against competitors-including those that may want to offer TV services to cable and phone company customers.

“I do believe that net neutrality ought to be the basic principle of whatever legislation we pursue,” said the lawmaker, who added that he wants to move a bill next month.

“I think we have to really understand what we’re talking about about net neutrality,” he said.

During hearings before the Senate Commerce Committee last week, representatives of the telephone and cable TV industries insisted that a new regulatory regime to prohibit them from abusing their rivals was unnecessary.

“We will not block, will not impair, will not degrade any content, any service, any application,” said Walter McCormick, president and CEO of the United States Telecom Association.

“Given the explosion of the Internet and its importance to our competitiveness, the creation of jobs, indeed our quality of life, the right call is to let the marketplace develop as it has without government regulation,” said Kyle McSlarrow, president and CEO of the National Cable & Telecommunications Association.

But critics warned that regulations are needed to prevent cable TV operators and phone companies from abusing their gatekeeper power.

“Allowing broadband carriers to control what people see and do online would fundamentally undermine the principles that have made the Internet such a success,” said Vinton Cerf, Google VP and chief Internet evangelist.

Added Earl Comstock, a top former aide to Sen. Stevens who is now president and CEO of the industry trade group Comptel, in written testimony: “As history has repeatedly demonstrated, it is only those who can discriminate who object to a requirement that they not do so.”

In a shot at critics, NCTA’s Mr. McSlarrow alleged that companies like Google-those he said that have flourished on the backs of the broadband networks of others-are promoting network neutrality to protect their own leadership in the market.

“They want to foreclose any new business model that would enable new entrants to challenge them,” Mr. McSlarrow said, adding that broadband providers might want to invest in businesses that could compete with Google.

USTA’s Mr. McCormick also said the phone companies believe competing services ought to help pay for the rollout of the new broadband networks.

“Simply put, our side believes that businesses that seek to profit on the use of next-generation networks should not be free of all costs associated with the increased capacity that is required for delivery of the advanced services and applications they seek to market,” Mr. McCormick said. “‘If you want more, then you pay more,’ is as American as it comes.”

At a McGraw-Hill Cos.-sponsored media conference in New York, Verizon Communications Chairman and CEO Ivan Seidenberg also promised that his company would never block consumers from accessing content.

He suggested it would be bad business for Verizon or any other broadband provider to exercise control over the content that consumers want to reach over high-speed Internet networks.

Jay Sherman contributed to this report.