An inquiry is being held into the death of Iraqi Baha Mousa
The only soldier convicted in connection with the death of Iraqi Baha Mousa claims that he witnessed an Army officer abuse other prisoners.
Former corporal Donald Payne told a public inquiry into Mr Mousa's death that he saw a group led by Lt Craig Rodgers "kick and/or punch" prisoners.
Mr Mousa, 26, died in Basra in 2003 while in the custody of the former Queen's Lancashire Regiment (QLR).
In a statement, Lt Rodgers denied the "utterly outrageous" allegations.
Payne also described the commanding officer of 1st Battalion QLR in Iraq in 2003, Lt Col Jorge Mendonca, as "gung-ho" and "somewhat trigger happy".
He said Lt Col Mendonca once held a cocked pistol above a prisoner's mouth and threatened to "blow his face off", and also shot out blacked-out car windows after a directive was issued banning them.
Caroline Hawley, BBC News, at the inquiry
It is not the first time Lt Rodgers has been implicated in the abuse, as soldiers who admit lying to an earlier court martial give evidence to this public inquiry.
Donald Payne clearly played a central role in the events that led to Baha Mousa's death but he says all members of the unit "emulated him" in kicking and punching detainees.
This inquiry seeks to discover not only who was responsible for the death but, crucially, who sanctioned the use of outlawed "conditioning techniques" including hooding, sleep deprivation and stress positions.
These did not, in themselves, lead to Baha Mousa's death, but their use seems to have helped create the environment in which "gratuitous violence" was allowed to occur. As Mr Payne gave evidence, Baha Mousa's father left the room in tears.
In a statement to the inquiry, Payne said: "He would pull his pistol out at any opportunity. He would behave as if he were a member of the SAS. Everyone knew and commented about his behaviour."
Payne became the first member of the UK armed forces to be convicted of a war crime when he pleaded guilty at a court martial to inhumanely treating civilians.
He served a year-long jail sentence, but no-one has ever been punished for causing the death of Mr Mousa, a hotel receptionist who was found to have suffered 93 separate injuries.
Lt Col Mendonca, who was later promoted to colonel, was cleared of negligently performing a duty at the same court martial, while five others were found not guilty of related charges.
His counsel, Tim Langdale QC, accused Payne of telling lies about his client at the inquiry.
Outside the hearing, Payne's solicitor William Bache told the BBC he hoped the inquiry would "tease out the truth" surrounding events and make clear where the blame lay.
"Some of that blame is likely to attach to senior officers, perhaps at brigade level, some... to the Ministry of Defence," he added.
In Iraq, Payne was part of a group - headed by Lt Rodgers - known by the call sign G10A.
Payne told the inquiry that he had covered up the extent of the abuse of Iraqis by British soldiers out of "misguided loyalty".
He previously claimed that he had only nudged or slapped detainees and never saw them being beaten by their guards.
In a statement, Payne told the inquiry: "I had regarded The Queen's Lancashire Regiment for over 18 years effectively as my family.
"I have known the disclosures I am about to make would harm the reputation of both my former regiment and the British Army and for these reasons have so far been unwilling to make them even to my lawyers.
Col Mendonca held a pistol above a detainee's mouth, it is alleged
"I now disclose that in adopting the routine I did, each time I returned to the temporary detention facility to ensure the detainees were awake, the degree of force I applied was greater than I have so far admitted.
"Moreover at one time or another I saw all the members of the multiple in call sign G10A emulate me."
Payne admitted that he lied "about almost everything" in interviews conducted during 2003 and 2004, had lied to the court martial and in his first statement to the public inquiry for reasons of "self-preservation".
He agreed with Gerard Elias QC, counsel to the inquiry, that the force had actually amounted to "an element of gratuitous violence" and later apologised to the detainees for his "appalling behaviour".
The former soldier suggested he beat the detainees because he believed - wrongly - that they were linked to the deaths of three Royal Military Police soldiers in Iraq in 2003.
Describing his struggle with Mr Mousa just before he died, Payne admitted putting his knee in the Iraqi's back to try to restrain him but denied banging his head against a wall.
The detainee was thrashing about when Payne heard his head "whack" against either the floor or the wall, he said.
Apart from claiming that G10A members assaulted the Iraqis, Payne said he also saw Lt Rodgers place a jerry can of petrol in front of a young boy.
"He poured water over him and then lit a match. Another member of the multiple was with Lt Rodgers but I do not now recall his identity," he said.
Lt Rodgers, who left the Army in March 2007, issued a statement in which he said the allegations were "simply untrue".
He added: "I have said before and say again that I did not mistreat any detainee in any way, and I categorically deny that I was anything to do with what Payne has alleged today."