The use of harsh interrogation techniques on detainees at Guantánamo Bay was a "mistake of massive proportions" that had damaged US national security, the former chief navy lawyer yesterday said.

Alberto Mora, formerly the navy general counsel who battled in the Pentagon to bar interrogation techniques such as waterboarding - -simulated drowning - described the interrogation programme as a "policy of cruelty" that "violated our founding values, our constitutional system . . . and our national security".