The US Federal Communications Commission has ordered Comcast to stop interfering with peer-to-peer traffic on its broadband network, with officials there saying the cable provider was "invasive" in its network traffic management.

In a victory for net neutrality advocates, the FCC on Friday voted 3-2 to order Comcast to stop slowing P-to-P traffic by the end of the year and to come up with a new network management plan. If Comcast refuses, the company could be subject to an injunction and other regulatory penalties.

Comcast's traffic management, unveiled by press reports in late 2007, was "discriminatory and not narrowly tailored to address Comcast's concern about network congestion," said FCC member Michael Copps. "Today, we choose the open road."

Comcast didn't tell its subscribers that it was slowing BitTorrent and other P-to-P traffic until the press reports. As expected, FCC Chairman Kevin Martin, a Republican, joined the commission's two Democrats to approve the order.

"Would you be OK with the post office opening your mail, deciding they didn't want to bother delivering it, and hiding that fact by sending it back to you stamped, 'address unknown -- return to sender?'" Martin said. "Or, if they opened letters mailed to you, decided that because the mail truck is full sometimes, letters to you could wait, and then hid both that they read your letters and delayed them? Unfortunately, that is exactly what Comcast was doing with their subscribers' Internet traffic."

Comcast continued to insist it was taking "carefully limited" network management measures. Four months ago, Comcast set a goal of creating a new network management policy by the end of the year, noted Sena Fitzmaurice, senior director of corporate communications and government affairs.

"We are gratified that the commission did not find any conduct by Comcast that justified a fine and that the deadline established in the order is the same self-imposed deadline that we announced four months ago," Fitzmaurice said. "On the other hand, we are disappointed in the commission's divided conclusion because we believe that our network management choices were reasonable, wholly consistent with industry practices and that we did not block access to Web sites or online applications, including peer-to-peer services."

The FCC order raises "a variety of substantive legal questions," and Comcast is considering all its legal options, she added.

The commission's two other Republicans argued that the FCC is interfering with Comcast's ability to protect its broadband network. Evidence gathered in the case is conflicting, and the decision may cause network gridlock, said FCC member Robert McDowell.

"The fact is the FCC does not know what Comcast did and did not do," he said. "Ironically, today's decision ... may result in slow speeds for 95 per cent of Internet users."

The order opens up the Internet to massive new regulation, McDowell added. Broadband providers may have to ask the FCC for permission to roll out new network management plans, he said.

In 2005, the FCC adopted Internet policy principles telling consumers they have a right to unfettered access to legal Web applications, devices and services of their choice. But those were guidelines, and the FCC lacks the authority to take action against Comcast, McDowell said. "We do not have any rules ... to enforce," he said.