The report challenges some widespread criticisms of armed drones. Arguing that they should neither be “glorified nor demonized,” it said there was strong evidence that civilian deaths from armed drone strikes are far fewer than from traditional combat aircraft. The panel also said there was little reason to conclude that drones create a “PlayStation mentality” — turning war into a video game that eliminates the psychological costs to drone pilots.

In fact, the report said, because drone pilots watch their targets sometimes for days and weeks before pulling the trigger — and then see them blown up on a high-resolution video screen — they are more susceptible to post-traumatic stress than pilots of manned aircraft.

The panel instead reserves the bulk of its criticism for how two successive American presidents have conducted a “long-term killing program based on secret rationales,” and how too little thought has been given to what consequences might be spawned by this new way of waging war.

The Obama administration has been reluctant to make public any of the legal underpinnings of the targeted killing program. As part of Freedom of Information Act lawsuits brought by the The Times and the American Civil Liberties Union, a federal appeals court this week released a redacted version of a 2010 Justice Department memo that blessed as legal the effort to kill Anwar al-Awlaki, the radical Muslim cleric and American citizen who died in a 2011 C.I.A. drone strike in Yemen. One section of the memo, a compilation of evidence to support administration claims that Mr. Awlaki had become an operational terrorist who posed a direct threat to Americans, remained redacted.

Some of the panel’s recommendations have already been embraced — although not yet adopted — by the Obama administration. One of the recommendations, shifting responsibility from the C.I.A. to the Pentagon for the bulk of drone operations, was first discussed by White House officials last May although the C.I.A. continues to carry out drone strikes in Pakistan and Yemen. It is unclear when, if ever, the C.I.A. will be taken off the mission of firing missiles from armed drones.

The panel’s recommendation that the government release information about drone victims follows a provision the Senate Intelligence Committee included in its authorization bill last year demanding that the Obama administration give an annual report about the number of militants and civilians killed and injured in drone strikes. But intelligence officials fought the provision and Senators quietly stripped it from the bill in April.

The report raised warnings that other countries might adopt the same rationale as the United States has for carrying out lethal strikes outside of declared war zones. Using an example of a current crisis, it said that Russia could use armed drones in Ukraine under the justification that it was killing anti-Russian terrorists and then refuse to disclose the intelligence that served as the basis for the strike.

“In such circumstances,” the report asked, “how could the United States credibly condemn Russian targeted killings?”