WASHINGTON — The nation’s top intelligence official on Wednesday delivered a scorching attack on Edward J. Snowden, the former National Security Agency contractor, and called on him and his “accomplices” to return the trove of classified documents he took from the N.S.A.

James R. Clapper Jr., the director of national intelligence, told lawmakers that Mr. Snowden’s disclosures had done grave damage to the country’s security and had led terrorist groups to change their behavior to elude American surveillance. Mr. Clapper did not give specific examples to bolster his assessment about the damage Mr. Snowden had done. He also did not say whom he believed Mr. Snowden’s accomplices to be.

In his annual testimony to Congress about the threats facing the United States, Mr. Clapper, who in the past has said he resented having to testify in public about classified issues, ticked off a daunting list: cyberattacks from China, Iran, North Korea and Russia; the spread of affiliates of Al Qaeda; and an array of nuclear, biological and chemical weapons technologies. But in part because he and his colleagues are so wary of discussing classified issues in public, the hearing became as much a moment for speechmaking as for substance.

Senator Ron Wyden, the Oregon Democrat who has been outspoken in his critique of the growth of the N.S.A.’s surveillance activities, said that the dealings between spy agencies and their congressional overseers were crippled by a “culture of misinformation.”