GENEVA: A United Nations investigator called on the United States on Monday to publish its findings on the CIA's Bush-era programme of rendition and secret detention of terrorism suspects.

Ben Emmerson, U.N. special rapporteur on the promotion and protection of human rights while countering terrorism, voiced concern that while President Barack Obama's administration has rejected Central Intelligence Agency practices conducted under his predecessor George W. Bush, there have been no prosecutions.

"Despite this clear repudiation of the unlawful actions carried out by the Bush-era CIA, many of the facts remain classified, and no public official has so far been brought to justice in the United States," Emmerson said in a report to the U.N. Human Rights Council, which he will address on Tuesday.

Emmerson, an international lawyer from Britain, has served since August 2011 in the independent post set up by the U.N. Human Rights Council in 2005 to probe human rights violations committed during counter-terrorism operations worldwide.

The "war on terror" waged by Bush after Al-Qaeda attacks on the United States on Sept. 11, 2001 led to "gross or systematic" violations involving secret prisons for Islamic militant suspects, clandestine transfers and torture, Emmerson said.

Under Obama, U.S. Attorney General Eric Holder said that the Department of Justice would not prosecute any official who acted in good faith and within the scope of legal guidance given by its Office of Legal Counsel in the Bush era on interrogation.

But Emmerson said that using a "superior orders defence" and invoking secrecy on national security grounds was "perpetuating impunity for the public officials implicated in these crimes".

A U.S. Senate select committee on intelligence, chaired by Democratic Senator Dianne Feinstein of California, investigated the CIA secret detention and interrogation programme, including use of "waterboarding", which simulates drowning.

Bush, who authorised the CIA's secret prisons overseas, said in his memoirs he had ordered the use of "waterboarding", which rights experts consider a form of torture banned by international law.

Emmerson said that the Senate panel was believed to have had unrestricted access to classified information for its comprehensive review, completed in December 2011.

He urged the U.S. government "to publish without delay, and to the fullest extent possible" the Senate report, except for any information strictly necessary to protect legitimate national security interests or the safety of people identified in it.

"BLACK SITES"

"There is now credible evidence to show that CIA 'black sites' were located on the territory of Lithuania, Morocco, Poland, Romania and Thailand, and that the officials of at least 49 other States allowed their airspace or airports to be used for rendition flights," Emmerson said, referring to clandestine sites where suspects were taken for detention without any extradition procedures, charges laid or access to a lawyer.

He urged those five states to conduct "effective independent judicial or quasi-judicial inquiries" into the allegations.

Any public officials who may have authorised or helped in setting up such facilities should be held accountable, he added.

Italy is the only country to have brought any public official to justice for such crimes, according to Emmerson.

In November 2009, the Milan criminal tribunal convicted 22 CIA agents in absentia for their role in the kidnapping of an Egyptian Muslim cleric known as Abu Omar on a Milan street in 2003 "and his rendition to Cairo where he was detained for 14 months and repeatedly tortured", the U.N. investigator said.

Emmerson also called on Britain to publish the 2012 interim report of the Gibson Inquiry set up two years earlier to probe whether its security or intelligence agents were involved in any mistreatment or rendition of detainees held by other countries.

In January he announced he would investigate the use of unmanned drones in counter-terrorism operations, after criticism of the number of innocent civilians killed.

Emmerson's non-binding report has only moral authority, but it will add pressure on the Obama administration not to allow what he called a "blanket of official impunity" to descend.