CAMBRIDGE, MA — Critics are bashing Comcast for fighting dirty as the Federal Communications Commission continues its investigation into whether broadband internet service providers selectively throttle users’ bandwidth.The administrative manager of Harvard University’s Berkman Center for Internet and Society accused Comcast of hiring “seat warmers” to prevent the public from attending an FCC hearing Monday at Harvard Law School. According to Catherine Bracy, about three dozen Comcast “ringers” arrived hours before the hearing was scheduled to start, and their presence in the limited available seats caused Comcast customers who may have wanted to address the hearing to be turned away.

Comcast disputed the allegation, admitting it hired people to hold seats for employees but adding the placeholders left when Comcast employees arrived to replace them. Comcast said it wanted to ensure the hearing wasn’t skewed unnecessarily toward the views of Free Press, a network neutrality advocacy group that had urged its supporters to attend.

“For the past week, the Free Press has engaged in a much more extensive campaign to lobby people to attend the hearing on its behalf,” Comcast said in a prepared statement released after Bracy made her allegation.

During the hearing, which was unusual in the fact that it was held outside the FCC’s Washington D.C. stomping grounds, Chairman Kevin Martin indicated the commission was willing to intervene on behalf of consumers if broadband ISPs are engaging in questionable traffic-management practices. Comcast and other ISPs have been accused of selectively limiting the bandwidth of users suspected of engaging in file-sharing on the assumption those users are tying up network resources while engaging in illegal activity. In 2005, the FCC developed a policy statement supporting so-called network neutrality — the proposition that all internet speech is equal and should not be controlled by those with the most power and money — but the ISP hearings represent the first opportunity the agency has had to demonstrate concrete support for the concept.

In the matter now before the FCC, carriers have asserted they must be allowed to clamp down on super-users of their bandwidth in order to ensure network availability for everyone else.

However, as Rep. Edward J. Markey (D-MA) remarked as he opened the hearing, “While carriers will assert the need to manage networks in their current state of evolution, we need to remember that Internet freedoms are most properly thought of as consumer-centric.”

Some critics have accused Comcast and other ISPs — notably Verizon — of using possibly dodgy network-management efforts to discourage upstarts from competing with communication giants’ video-on-demand and other entertainment offerings.

“These are very significant issues, and we don’t take those allegations lightly,” Martin said during the hearing. “The commission is ready, willing and able to step in and correct any practices that are ongoing today.”

The FCC chief’s comments were hailed as paving the way for legislative action to ensure network neutrality.

“Martin has never had a clearly elucidated position on this, but we’re seeing what Martin thinks now and he has the swing vote on this,” Tim Wu, a professor of law at Columbia University, told the Washington Post after he testified at the hearing. “He thinks that it’s a consumer-rights issue; whether that is a principle for the ages or principle for the case we don’t know, but he certainly sent a message.”