Shocking photographs apparently showing British troops torturing an Iraqi detainee have been published.
The Ministry of Defence launched an immediate investigation into the alleged incident which was condemned as "shameful" by the army's most senior officer and the British Prime Minister, Mr Tony Blair.
The pictures, printed in the Daily Mirror, show soldiers apparently beating the man - a suspected thief - with rifle butts and urinating on him.
He was allegedly threatened with execution during an eight-hour ordeal, which left him bleeding and vomiting, with a broken jaw and smashed teeth.
Chief of General Staff General Sir Michael Jackson said: "I am aware of the allegations which have been made of the abuse of prisoners by British soldiers in Iraq.
"If proven, not only is such appalling conduct clearly unlawful, but it also contravenes the British Army's high standards.
"All allegations are already under investigation. If proven, the perpetrators are not fit to wear the Queen's uniform. They have besmirched the good name of the Army and its honour.
"Most emphatically, the British army should not be judged by the reprehensible ill-discipline of a few soldiers who, by their shameful behaviour, have let down those tens of thousands of British soldiers who have worked, and still do, in difficult and dangerous conditions in the most commendable way, in particular in Iraq, where their sole purpose is to help the Iraqis to a new and better future."
The Mirrorsaid it was given the pictures by serving soldiers from the Queen's Lancashire Regiment, who were horrified at the act depicted and concerned that "rogue elements" in the army were undermining attempts to win the hearts and minds of local people in British-administered southern Iraq.
Speaking on condition of anonymity, the soldiers told the paper that the unnamed captive, against whom no charges were brought, was driven away and dumped from the back of a moving vehicle following his ordeal. It was not known whether he survived.