Comcast's slowing of peer-to-peer traffic appeared to be more widespread than the company has disclosed, the chairman of the U.S. Federal Communications Commission said Tuesday.

FCC chairman Kevin Martin, testifying before a Senate committee, said Comcast's blocking of BitTorrent peer-to-peer traffic appeared to happen when there wasn't network congestion, in contrast to claims from the broadband provider. Comcast's actions, first described by the Associated Press last October, appeared to "block uploads of a significant portion of subscribers" in that part of the network, even during times when the network wasn't congested, Martin said.

"It does not appear that this technique was used only to occasionally delay traffic at particular nodes suffering from network congestion at that time," Martin told the Senate Commerce, Science and Transportation Committee. "Based on testimony we've received thus far, this equipment was typically deployed over a wider geographic area or system, and is not even capable of knowing when an individual ... segment of the network is congested."

The FCC is currently investigating Comcast's network management practices and has held two hearings about the complaints.

A Comcast spokeswoman issued a statement, repeating the company's assertion that it was slowing p-to-p traffic in a limited setting.

"As has always been our policy, Comcast does not, has not, and will not block any websites or online applications, including peer-to-peer services," the statement said. "We have acknowledged that we manage peer-to-peer traffic in a limited manner to minimize network congestion."

Comcast described its network management as a "reasonable choice," but it also announced in March that it would work with BitTorrent and other companies to move to protocol-agnostic network management by the end of the year.

Martin resisted calls by Democratic members of the committee to pass a network neutrality law, saying the FCC now has the authority to act on network blocking complaints on a case-by-case basis. The FCC in 2005 adopted a set of open Internet policy principles, and it has responded to traffic-blocking complaints, Martin said.

But Democratic Sens. John Kerry of Massachusetts and Bryon Dorgan of North Dakota noted that Comcast, in a recent FCC filing, disputed the FCC's authority to act on content-blocking complaints. "You're looking at a lawsuit" if you act on the complaints against Comcast, Kerry said.

A net neutrality law passed by Congress would clarify the FCC's authority to act on content-blocking complaints, Kerry and Dorgan said.

But several Republican members of the committee said an extensive net neutrality law could have unintended consequences and could hamper innovation and new business models.

"If the Internet has taught us anything, it's that it's pretty presumptuous to predict what the future will be," said Sen. John Sununu, a New Hampshire Republican. "We should be very, very cautious about imposing regulations based on what we think competitors will do in the future and how we think consumers will respond based on what we think competitors will do."