The newspaper defended its decision to publish the photos over the weekend, with a statement from editor Piers Morgan, who wrote "The Mirror makes no apology for exposing this outrageous and unlawful behavior" in which photos show a hooded prisoner being urinated on and beaten with rifle butts.
The pictures were published Saturday, and allegations they had been faked came quickly from an opposition Conservative spokesman and a BBC correspondent.
One of two unidentified soldiers from the Queen's Lancashire Regiment present when the pictures were taken told the newspaper "This happened, it is not a hoax and the Army knows a lot more has happened."
An unnamed officer told GMTV Sunday that senior ranks had turned a "blind eye" to mistreatment of Iraqi prisoners.
"People were literally getting serious beating or kickings ... you're talking broken ribs, punctured lungs sort of thing," the officer said.