Seven former heads of the United States Central Intelligence Agency are calling on President Barack Obama to halt a probe into alleged abuses during the interrogation of terror suspects. They argue that the investigation could jeopordise the effectiveness of future intelligence work.

Last month, Attorney General Eric Holder appointed a special prosecutor to investigate possible crimes committed by CIA agents. Some of them allegedly used death threats and fake executions during interrogations. Former president George W Bush refused to allow the accusations to be investigated.