The United Nations' top special investigator for counterterrorism is calling for the prosecution of senior U.S. officials who authorized and carried out torture as part of former President George W. Bush's national security policies.

Ben Emmerson, the U.N.'s special rapporteur on counterterrorism and human rights, says all CIA and other U.S. government officials who carried out waterboarding and other torture must also be prosecuted.

In a statement Wednesday released in Geneva, Emmerson said the U.S. Senate Intelligence Committee's report shows "there was a clear policy orchestrated at a high level within the Bush administration, which allowed (it) to commit systematic crimes and gross violations of international human rights law."

He says those responsible for the "criminal conspiracy ... must face criminal penalties commensurate with the gravity of their crimes."