Two Democrats in the US House of Representatives have introduced a bill that would subject broadband providers to antitrust violations if they block or slow Internet traffic.

Representative John Conyers, a Michigan Democrat and chairman of the House Judiciary Committee, has sponsored the Internet Freedom and Nondiscrimination Act along with Representative Zoe Lofgren, a Democrat from the Silicon Valley area of California.

The legislation requires Internet service providers to interconnect with the facilities of other network providers on a reasonable and nondiscriminatory basis. It also requires them to operate their networks in a reasonable and nondiscriminatory manner so that all content, applications and services are treated the same and have an equal opportunity to reach consumers.

Any ISPs that do not follow these net neutrality rules would be subject to antitrust enforcement.

The legislation, introduced Thursday, earned praised from some consumer and online rights groups. Large broadband and mobile phone service providers have begun to discriminate against some content, with Comcast saying it has slowed some customer access to the BitTorrent peer-to-peer protocol during times of network congestion, they say. Other broadband providers have talked about managing their networks or asking some popular Web sites to pay more for fast service, net neutrality advocates have said.

"The bill squarely addresses the issue of the enormous market power of the telephone and cable companies as the providers of 98 percent of the broadband service in the country," said Gigi Sohn, president of Public Knowledge. "The bill restores the principle of nondiscrimination that allowed the Internet to flourish in the dial-up era, making certain that the same freedom and innovation will flourish in the broadband era without burdensome regulation."

But broadband providers and some congressional Republicans have argued that net neutrality legislation isn't necessary. The broadband market is becoming more competitive and net neutrality regulations could hamper investment in broadband networks, some Republicans said during a hearing this week.

Competition is happened at "all levels of the Internet," Representative Fred Upton, a Michigan Republican, said this week. "Our hands-off policy is working."

Conyers and Lofgren were cosponsors of a similar bill introduced in 2006, when Republicans held a majority in the House. With significant Republican opposition, the 2006 bill died, but Democrats were elected to the majority late that year.

"Americans have come to expect the Internet to be open to everyone," Conyers said in a statement. "The Internet was designed without centralized control, without gatekeepers for content and services. If we allow companies with monopoly or duopoly power to control how the Internet operates, network providers could have the power to choose what content is available."