No private contractors have so far faced prosecution despite their implication in the Abu Ghraib prisoner abuse scandal in Iraq, according to a new Pentagon report.

The study, sent to Congress earlier this year but not publicly released, covers the period from the start of May 2003 to the end of October 2004. It was ordered by Congress last year in the immediate aftermath of the Abu Ghraib scandal, in which it emerged that employees of private contractors were directly involved in interrogating Iraqi detainees.