The CIA has used "stress and duress" techniques on al-Qaida suspects held at secret overseas detention centres, as well as contracting out their interrogation to foreign intelligence agencies known to routinely use torture, said a report published yesterday.

The Washington Post paints a harrowing picture of the procedures for extracting information from terrorism suspects at such centres as Diego Garcia, the Indian Ocean island leased from Britain, and Bagram, the large US airbase in Afghanistan.

Inmates at Bagram are kept in painful positions for hours, hooded or made to wear opaque goggles, or bombarded with light, the report says. However, other detainees have faced far worse for not cooperating, being "rendered" to a foreign intelligence service which has no compunction about torture.

The Post suggests there has been a sweeping change in US policy on torture since September 11, despite public pronouncements against its use. It quotes Cofer Black, the former director of the CIA's counter-terrorist branch, as telling a congressional intelligence committee: "All you need to know: there was a before 9/11, and there was an after 9/11... After 9/11 the gloves come off."

Yesterday's report has deepened concern in human rights circles about the fate of the roughly 3,000 people quietly detained around the world.

"I think there needs to be a clear statement from the US government that they are abiding by the Geneva convention with the treatment of detainees," James Ross, a senior legal adviser at Human Rights Watch, said yesterday.

"Turning people over to another government to do something that would amount to torture is a problem. It is torture by proxy, and the US should not be doing that."

The CIA refused to comment on the report yesterday.

Reports that there could be abuse of detainees at Diego Garcia could also prove embarrassing for Britain. The Indian Ocean atoll is a British dependency and houses joint US and British air and naval facilities.

"If they know about this, and torture and mistreatment are taking place in Diego Garcia, British officials could also be viewed as taking part in torture," Mr Ross said.

The report offers the first details of inmates' treatment at CIA camps outside Guantanamo Bay, where some 600 al-Qaida suspects are held. But the Guantanamo inmates have had at least limited access to lawyers, journalists, and the Red Cross, whereas Bagram is strictly off-limits, and human rights groups fear conditions could be worse.

Earlier this month, officials said they would launch a criminal inquiry into the death of two prisoners at Bagram. One reportedly died of a heart attack, the other of a pulmonary embolism.

US laws apparently do not apply at the centres, where CIA agents oversee - or take part in - the interrogations. While the US publicly denounces torture, the Post says each of the 10 serving national security officials interviewed by the paper defended the use of violence against captives.

"If you don't violate someone's human rights some of the time, you probably aren't doing your job," an official who has supervised the capture of suspects told the newspaper. "I don't think we want to be promoting a view of zero tolerance on this. That was the whole problem for a long time with the CIA."

The report says CIA agents sometimes trick a detainee into thinking he is held in a state where torture is routine. On other occasions, low-level suspects have been handed over to Jordanian, Egyptian, and Moroccan agencies - known for their brutality - with a list of questions from the CIA.

Some US officials claim the main motive of such "renditions" is the belief that a suspect will open up if questioned in his own language or on familiar terrain.

However, one official directly involved in rendering captives to foreign hands is quoted as saying: "We don't kick the [expletive] out of them. We send them to other countries so they can kick the [expletive] out of them."