The most common mistreatment reported by soldiers and marines was that of insulting non-combatants in their presence, the report said.
The survey showed that 55 per cent of US army soldiers, and only 40 per cent of marines, would report a fellow serviceman for killing or injuring an innocent non-combatant.
The survey, which shows increasing rates of mental health problems for troops on extended or multiple deployments in Iraq, was the first to include questions on ethics and ethical training.
As such, the report stresses the findings cannot be compared "with any other group of military personnel".
The 89-page report found that the US troops surveyed had on average:
Insulted or cursed at non-combatants in their presence:
Marines - 30%
Soldiers - 28%
Damaged or destroyed Iraqi property when it was not necessary:
Marines - 12%
Soldiers - 9%
Physically hit or kicked non-combatants when it was not necessary:
Marines - 7%
Soldiers - 4%
More than a third of the 1,320 soldiers and 447 marines surveyed said that torture should be allowed to save the life of a fellow soldier or marine, while almost 38 per cent said torture should be allowed in order to gather "important information about insurgents".
"These men and women have been seeing their friends injured and I think that having that thought is normal," said Pollock, but she added: "They're not acting on those thoughts. They're not torturing the people."
The survey showed only 47 per cent of soldiers and 38 per cent of marines agreed that non-combatants should be treated with dignity and respect.
US operations in Iraq have been dogged by claims of mistreatment of Iraqi detainees and civilians, including revelations of abuse at Abu Ghraib prison in 2004 and reports of the killing of 24 Iraqi civilians by Marines in Haditha in November 19, 2005.
|Only 47 per cent of soldiers agreed non-|
combatants should be treated with dignity [EPA]
The main aim of the report was to assess the mental health of soldiers and marines involved in operations in Iraq.
The report showed the rate of anxiety, depression and acute stress stood at 22 per cent among soldiers deployed in Iraq for more than six months.
It also recorded an average of 16.1 suicides per year per 100,000 soldiers for those involved in Operation Iraqi Freedom.
Overall, about 20 per cent of army soldiers and 15 per cent of marines showed mental health symptoms of either anxiety, depression or acute stress.
Among army soldiers, 27 per cent of those with more than one tour of duty tested positive for a mental health problem, versus 17 per cent for soldiers on their first deployment.
Morale among soldiers was worse than among marines, which it said was explained in part by the marines' shorter six month tours.
The report recommended that the army's year-long tours in Iraq either be shortened or soldiers be given 18 to 36 months between deployment to recover.
But instead, the army is moving in the opposite direction, with Robert Gates, the US defence secretary, announcing extended tours for US soldiers in Iraq and Afghanistan of up to 15 months instead of one year.
The army is struggling to allow units a year at home between deployments.
The survey was conducted by US army medical experts between August 28 and October 3, last year.
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