The Guardian, Monday 7 January 2013 16.25 GMT
The United States' use of drones is counter-productive, less effective than the White House claims and is "encouraging a new arms race that will empower current and future rivals and lay the foundations for an international system that is increasingly violent", according to a study by one of President Obama's former security advisers.
Michael Boyle, who was on Obama's counter-terrorism group in the run-up to his election in 2008, said the US administration's growing reliance on drone technology was having "adverse strategic effects that have not been properly weighed against the tactical gains associated with killing terrorists".
Civilian casualties were likely to be far higher than had been acknowledged, he said.
In an article for the Chatham House journal International Affairs, Boyle said the conventional wisdom over the use of unmanned aerial vehicles (UAVs) needed to be challenged.