Ben Griffin was a member of the elite SAS. He told his commanding officer, earlier this year, that he was not prepared to return to Iraq because he said he saw American forces carrying out what he thought were illegal acts.
He was allowed to leave the military and he now says: "I was disturbed by the general day-to-day attitude of the American troops. They treated Iraqis with contempt, not like human beings. They had a complete disregard for Iraqi lives and property."
Mr Griffin would never have considered deserting but he says that his views are shared by many others in the British military.
He told the BBC: "I can't speak for others but there's a lot of dissent in the Army about the legality of war and concerns that they're spending too much time there".
He says Iraq is different to other conflicts because, in other operations, the main aim is to improve life for the local population and he believes that is not what has happened in Iraq.
Mr Griffin says: "There's contempt for the locals. We don't even know how many have been killed."
His advice to others is not to desert - but that if they have doubts, they should follow their conscience, speaking out if they think that the Iraq conflict is wrong.