In an interview with The Signal newspaper of Santa Clarita, California, which was also broadcast on a local television channel yesterday, Gen Karpinski was asked if she knew of documents showing that Mr Rumsfeld approved "particular interrogation techniques" for Abu Ghraib.

    Gen Karpinski was interviewed for four hours by Maj- Gen Antonio Taguba, who was ordered to investigate abuse at Abu Ghraib and produced a damning report, which heavily criticised Gen Karpinski for a lack of leadership at the prison.

    During inquiries into the scandal, she has repeatedly maintained that the treatment of Iraqi detainees was taken out of her hands by higher-ranking officials, acting on orders from Washington.

    "Since all this came out," she replied, "I've not only seen, but I've been asked about some of those documents, that he [Mr Rumsfeld] signed and agreed to."

    Asked whether the documents have been made public, Gen Karpinski replied "No" and went on to describe the methods approved in them as involving "dogs, food deprivation and sleep deprivation".

    The Pentagon has consistently denied that Mr Rumsfeld authorised the transfer of harsher techniques of interrogation and detention from Guantánamo Bay to Abu Ghraib, where all prisoners are supposed to be protected by the Geneva Conventions.

    Replying to Gen Karpinski's allegations, a spokesman for the Pentagon told The Telegraph: "Mr Rumsfeld did not approve any interrogation procedures in Iraq. The Secretary of Defence was not in the approval chain for interrogation procedures, which would have remained within the purview of Central Command, headed by Gen John Abizaid."

    The Bush administration has been dogged by suspicions that harsh interrogation methods employed at Guantanamo were transferred to Abu Ghraib, as Iraqi insurgents began to score significant hits against coalition forces last year. In May, before the Senate armed services committee, Stephen Cambone, the under-secretary of defence for intelligence, publicly denied charges that Mr Rumsfeld had approved Guantanamo-style interrogations in Iraq.

    Last month, the White House took the unusual step of releasing hundreds of internal documents and debates concerning interrogation procedures at Guantánamo. Extreme interrogation techniques at the camp, it was revealed, now require the explicit approval of Mr Rumsfeld. The Bush administration insists, however, that the notorious abuse of prisoners at Abu Ghraib was an aberration on the part of a handful of rogue soldiers. A Pentagon spokesman said that all relevant documents on interrogation techniques in Iraq would be made public but could not say when.

    Gen Karpinski has been suspended from duty pending ongoing investigations into abuse of prisoners at the Baghdad prison. In a recent interview with the BBC, she complained of being turned into a scapegoat for the scandal, arguing that the running of the prison was taken out of her hands.

    In a separate embarrassment for the Department of Defence last week, six recent studies, leaked to the Los Angeles Times, heavily criticised the military for failing to screen adequately potential recruits with violent and even criminal backgrounds.

    The reports were written by a senior Pentagon consultant. One was delivered in September 2003, weeks before the worst abuses of Iraqi prisoners took place. The title of the report was Reducing the Threat of Destructive Behaviour by Military Personnel.

    In it the author, Eli Flyer, a former senior analyst at the Department of Defence, stated: "There are military personnel with pre-service and in-service records that clearly establish a pattern of sub-standard behaviour. These individuals constitute a high-risk group for destructive behaviour and need to be identified."

    According to a 1998 report by Mr Flyer, one third of military recruits had arrest records. A 1995 report found that a quarter of serving army personnel had committed one or more criminal offences while on active duty. In his 2003 study, Mr Flyer said that military personnel officers had been reluctant to toughen up screening procedures, fearing that the result would be a failure to meet recruitment goals.

    Curtis Gilroy, who oversees military recruiting policy for the Pentagon, told the Los Angeles Times: "It's hard to pick out all the bad apples, but we are striving to improve the system and are doing so."