An internal investigation by the C.I.A. has found that its officers penetrated a computer network used by the Senate Intelligence Committee in preparing its damning report on the C.I.A.'s detention and interrogation program. The report by the agency's inspector general also found that C.I.A. officers read the emails of the Senate investigators and sent a criminal referral to the Justice Department based on false information. The investigation also discovered that the officers created a false online identity to gain access on more than one occasion to computers used by the committee staff. The inspector general's account of how the C.I.A. secretly monitored a congressional committee charged with supervising its activities touched off angry criticism from members of the Senate and amounted to vindication for Senator Dianne Feinstein of California, the committee's Democratic chairwoman, who excoriated the C.I.A. in March when the agency's monitoring of committee investigators became public. Senator Mark Udall, Democrat of Colorado and another member of the Intelligence Committee, demanded Mr. Brennan's resignation. The C.I.A. unconstitutionally spied on Congress by hacking into the Senate Intelligence Committee computers," he said in a written statement. "This grave misconduct not only is illegal but it violates the U.S. Constitution's requirement of separation of powers," he added.