A British paratrooper commended for bravery in Iraq helped trigger the brutal attack in which six Red Caps died, a BBC documentary has claimed.
Some of the six who died were about to head back to the UK
The programme, Sweeney Investigates, said Cpl John Dolman fired shots which exacerbated the riot in which the six men died in southern Iraq in 2003.
Cpl Dolman, who left the Army last year to work for a security firm, was killed in a Baghdad suicide bomb in January.
An MoD inquiry into the deaths found they could not have been prevented.
Some of the men's families accused the MoD of a cover-up and called for an independent inquiry.
The programme said Cpl Dolman had been previously investigated for the killing of two civilians in Kosovo.
The six Royal Military Police officers were killed on 24 June, 2003 after becoming trapped in a police station by an angry crowd in Al Majar Al Kabir, near Basra.
Paras had fled the area after a fierce firefight, not realising the Red Caps were in the town.
The documentary said that two days before the incident, paras had to fire warning shots after a crowd started throwing stones at them.
The following day the troops signed a deal with local leaders agreeing not to perform weapons searches in the area.
RED CAPS KILLED
Sgt Simon Hamilton-Jewell, from Chessington, Surrey
Cpl Russell Aston, from Swadlincote, Derbyshire
Cpl Paul Graham Long, from Colchester, Essex
Cpl Simon Miller, from Washington, Tyne & Wear
L-Cpl Benjamin John McGowan Hyde, from Northallerton, North Yorkshire
L-Cpl Thomas Richard Keys, from Bala, Wales
The programme said Iraqis thought that meant there would be no patrols at all, but the troops assumed regular checks could continue.
When the paras entered the town on 24 June, they were attacked.
Cpl Dolman later testified to the Army board of inquiry that he had fired a rubber bullet at a man he believed to be one of the leaders of the attack.
"I had to load and hit him. In a built-up area, firing one of those sounds worse than it is.
"Looking back, they obviously thought it was a couple of bullets."
A firefight then broke out between the paras and about 100 Iraqis, the programme said.
While the paras were able to leave, the Red Caps, who had come to the town to ask local police why they had not intervened in the stoning incident two days before, were trapped and murdered.
Cpl Dolman, a father of two originally from Ollerton, Nottinghamshire, was killed on 3 January while working for Kroll Inc in the Iraqi capital.
He was investigated by the Military Police over the Kosovo shootings, however no charges were brought, the documentary said.
It said two survivors successfully sued the MoD at a civil trial over the incident.
The ministry was ordered to pay an estimated £100,000 in damages.
The programme quoted the judge in the case as saying: "The Queen's uniform is not a licence to commit a wrongdoing."
The inquiry into the Red Caps' deaths did not consider the Kosovo incident.
The MoD said the inquiry came to its conclusions "based on the facts".
Sweeney Investigates: the death of the Red Caps, was broadcast on BBC Two on Thursday, 10 February at 2150GMT.