A senior British army officer is being investigated over allegations that he mistreated prisoners of war in Iraq, the Ministry of Defense (search) said Wednesday.

Defense sources said the officer under investigation is Lt. Col. Tim Collins, who made headlines on the eve of battle with a stirring speech to his troops urging them to fight with honor. The allegations were made by U.S. troops attached to his 1st Battalion of the Royal Irish Rangers (search), the sources said.

The army's Special Investigations Branch is probing allegations that Collins' treatment of prisoners of war and an Iraqi civic leader may have violated the Geneva Conventions (search), the sources said on condition of anonymity.

The British Broadcasting Corp. Web site reported that Collins, who is on leave as he awaits a new army posting, said Wednesday he was confident his reputation would be upheld. Collins made no other public statement.

The Sun newspaper, which reported the allegations, said Collins had denied any wrongdoing. The paper said Collins allegedly punched, kicked and threatened prisoners to get information and fired shots at the ground to intimidate them, and that he allegedly hit the civic leader with the butt of a pistol.

The Evening Standard newspaper said the complaints were made by U.S. reservists who came under Collins' command in Iraq. The newspaper quoted unidentified witnesses who said the American soldiers were angry about the severe discipline imposed on them by Collins, who is known for his blunt and direct leadership style.

The Defense Ministry confirmed the investigation into an officer serving in Iraq but declined to identify the officer or detail the allegations involved in the investigation.

The ministry said Collins, who commanded the 1st Battalion of the Royal Irish Rangers, had left his regiment and was on operational leave while waiting for his appointment to another post.

Col. Bob Stewart, the former commander of British Forces in Bosnia, said an investigation was appropriate to keep the army beyond reproach but said there were situations in war that could be interpreted in different ways.

Stewart described slapping a hysterical woman during the conflict in Northern Ireland.

"I hated myself for doing it but it was the only way that I could get her under control. I do not think it was a war crime. I did it deliberately and I did it to get the situation under control," he said.

"I can readily see situations where people do things that can be cut any way you like."

Collins, 43, who was often seen with a cigar clenched between his teeth and wearing sunglasses, was the commanding officer of the 1st Battalion of the Royal Irish Regiment.

He galvanized his troops on the eve of battle with a speech in Kuwait in which he urged them to do their duty while treating the enemy with respect.

"Wipe them out if that is what they choose. But if you are ferocious in battle remember to be magnanimous in victory," he said.

"... If you harm the regiment or its history by over-enthusiasm in killing or in cowardice, know it is your family who will suffer. You will be shunned unless your conduct is of the highest."

Prince Charles was so impressed by the speech that he wrote a personal note to Collins to say how "profoundly moved" he was by the "extraordinarily stirring, civilized and humane" words.

President Bush was reported to have a copy of the speech at the Oval Office.