( CNN ) -- The United States has created a `` zone of impunity '' by rarely investigating private contractors involved in the unlawful killing of civilians in Afghanistan and Iraq , a U.N. human rights envoy said . Civil rights activists protest the use of unmanned U.S. drones in Pakistan . The U.S. government should track the number of civilians killed in its military operations abroad and limit collateral damage from unmanned drone attacks , Special Investigator Philip Alston said in a stinging report submitted Wednesday to the U.N. Human Rights Council in Geneva , Switzerland . `` The government has failed to effectively investigate and punish lower-ranking soldiers for such deaths , and has not held senior officers responsible , '' Alston said . `` Worse , it has effectively created a zone of impunity for private contractors and civilian intelligence agents by only rarely investigating and prosecuting them . '' Alston recommended that the United States establish a national commission to independently look into the policies and practices that are leading to the deaths . He also urged that an independent special prosecutor be charged with pursuing criminal allegations against government officials accused of wrongdoing . `` First , the government has failed to track and make public the number of civilian casualties , or the conditions under which deaths occurred , '' he said . `` Second , the military justice system fails to provide ordinary people , including U.S. citizens and families of Iraqi and Afghan victims , basic information on the status of investigations into civilian casualties or prosecutions resulting therefrom . '' Alston called the United States ' reliance on pilotless missile-carrying aircraft `` increasingly common '' and `` deeply troubling . '' U.S. forces operating in Afghanistan have used drones to attack militant targets in Pakistan . Pakistan has said the attacks have claimed hundreds of civilian lives . Mark Cassayre , the American representative to the U.N. Human Rights Council , said U.S. military and intelligence operations during armed conflict did not fall within the special investigator 's mandate . Alston is the special investigator on extrajudicial , summary or arbitrary executions . `` We wish to be clear that the prosecution of private contractors who commit crimes is an important priority of the Department of Justice , and despite the difficulty of these cases , the United States continues to attempt to bring private contractor cases to justice , '' Cassayre said .
U.N. envoy rips U.S. over investigation into drone attacks overseas . Private contractors protected by `` zone of impunity , '' envoy says . Score: 7