The top U.S. communications regulator said on Tuesday that an investigation of how Comcast manages its network had raised further concerns about tactics the company has used to restrict Internet users who share movies and other material.

Testifying before Senate lawmakers, U.S. Federal Communications Commission Chairman Kevin Martin said Comcast had used a "blunt" technique to impose broad restrictions on peer-to-peer file-sharing.

"Contrary to some claims, 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 said in prepared remarks before the Senate Commerce Committee.

Martin also disputed the claim by Comcast that the FCC does not have the legal authority to enforce its open-Internet policy. He told the committee that the agency does not need any new laws or regulations to take action.

"I do not believe any additional regulations are needed at this time. But I also believe that the commission has a responsibility to enforce the (open-Internet) principles that it has already adopted," Martin said.

The FCC is looking into complaints from consumer groups that cable operator Comcast violated those principles by unreasonably hindering some file-sharing services, such as BitTorrent, that distribute TV shows and movies.

Comcast issued a statement on Tuesday reiterating that it believes its network management practices were a "reasonable choice" and saying that it was switching to a new technique by the end of the year.