Fresh allegations of abuse of Iraqi prisoners by UK soldiers have been uncovered by BBC Two's Newsnight.
The allegations relate to British forces in Basra
Two brothers claim they were beaten and denied water and sleep after they were arrested in Basra and taken to a camp, weeks after military action began.
Marhab and As'ad Zaaj-al-Saghir have not made an official complaint, but have asked to be compensated for the car and cash they say UK troops seized.
The Ministry of Defence said it only investigated claims reported to it.
A spokeswoman urged anyone with evidence of abuse to come forward so the allegations could be looked into.
Marhab Zaaj-al-Saghir told the programme: "They lowered me down... while I was tied up, threw me on the floor and hit me with a stick.
"You couldn't draw breath afterwards and I lost consciousness."
He said he had then been urinated on.
His brother As'ad also claimed he was tied up and abused.
Another man, Hani Jahoush, said he was held for more than two months without charge.
He told Newsnight he was punched and chased with a whip as he moved around his cell.
He also claimed he was forced to make monkey noises and threatened with an electric shock machine.
A soldier is due to be tried for the manslaughter of Baha Mousa
Newsnight says the men's accounts are similar to many others recounted in a confidential report by the International Committee of the Red Cross.
It says that according to the report, inmates at the camp at Umm Qasr, where the men were held, "were routinely treated by their guards with general contempt, with petty violence".
According to the MoD, 177 investigations into alleged abuse by British troops have been carried out.
Of those 156 have been closed with no further action taken.
The bulk of the investigations - 100 cases - dealt with incidents where the Army say they returned gunfire after they were attacked.
Others involved traffic incidents alleged to have been caused by British troops.
Only five investigations stemmed from serious complaints of abuse in detention, the MoD told Newsnight.
One of those concerned allegations of abuse at Camp Breadbasket in Basra, over which three soldiers were convicted.
Last month seven soldiers were charged in connection with the death of Iraqi hotel receptionist Baha Mousa.
One of the soldiers is awaiting trial charged with his manslaughter.
But the lawyer representing the family of Mr Mousa says he is dealing with another dozen claims of unlawful killing and 50 of torture and beatings.
Basra-based Bassam al-Tamimi says the Army has looked into 20 of these and either offered some compensation or concluded there was no case to answer.
He also said it was difficult to ensure information about claims reached the Army's legal department or senior officers.
This was because documents were shredded or thrown into the bin, he alleges.
The MoD defended its record on investigating claims of wrongdoing by British forces.
A spokesman said: "We have a robust system for investigating incidents involving the death, injury or alleged ill-treatment of civilians on operations.
"All serious allegations reported to the military authorities are investigated by service police.
"The Army has shown its determination to investigate allegations of serious wrongdoing, and, where there is sufficient evidence, to call individuals to account before the courts."
The investigation will be shown on BBC Two's Newsnight at 2230 BST on Tuesday.