WASHINGTON  The new chairman of the House Homeland Security Committee said Monday that he planned to call mostly Muslim and Arab witnesses to testify in hearings next month on the threat of homegrown Islamic terrorism.

Representative Peter T. King, Republican of New York, said he would rely on Muslims to make his case that American Muslim leaders have failed to cooperate with law enforcement officials in the effort to disrupt terrorist plots  a claim that was rebutted in recent reports by counterterrorism experts and in a forum on Capitol Hill on Monday.

“I believe it will have more of an impact on the American people if they see people who are of the Muslim faith and Arab descent testifying,” Mr. King said.

The hearings, which Mr. King said would start the week of March 7, have provoked an uproar from both the left and the right. The left has accused Mr. King of embarking on a witch hunt. The right has accused him of capitulation for calling Muslims like Representative Keith Ellison, Democrat of Minnesota, to testify while denying a platform to popular critics of Islamic extremism like Steven Emerson, Frank Gaffney, Daniel Pipes and Robert Spencer.