A civilian who died in British custody in 2003 in Iraq suffered "an appalling episode of serious gratuitous violence" at the hands of British soldiers, an independent inquiry found on Thursday.

The treatment of 26-year-old hotel receptionist Baha Mousa represented a "very serious breach of discipline" by members of the army, said retired judge William Gage, who led the three-year probe.

Mousa, a father of two, died on September 15, 2003, about 36 hours after being detained in Basra along with nine other suspected insurgents by soldiers from 1st Battalion the Queen's Lancashire Regiment (1QLR).

Mousa sustained 93 separate injuries, including fractured ribs and a broken nose, during his time in custody.

The inquiry found his death was caused by a combination of his injuries -- some of which were sustained during a final violent assault by one soldier, Donald Payne -- and his weakened physical state due to his detention.

Mousa and the other Iraqi detainees were hooded, handcuffed and held in stress positions by the British soldiers, and they were also subjected to a "dreadful catalogue of unjustified and brutal violence" by Payne, the inquiry said.

Payne has already been convicted over the abuse. During a court martial in 2006-07, he pleaded guilty to inhumanely treating civilians, becoming the first member of the British armed forces convicted of a war crime.

Although the use of hooding and painful stress positions were banned by the British government in 1972, Gage found a lack of knowledge of this prohibition, which he blamed on "corporate failure" by the Ministry of Defence.

The inquiry chairman said such practices were "standard operating procedure" among 1QLR soldiers dealing with suspected Iraqi insurgents, but said they were "wholly unacceptable in any circumstances".

Gage concluded that the abuse "constituted an appalling episode of serious gratuitous violence on civilians which resulted in the death of one man and injuries of others".

"They represent a very serious breach of discipline by a number of members of 1QLR," he continued, adding that the events were "a very great stain on the reputation of the army".