A secret deal between Britain and the notorious al-Mahdi militia prevented British Forces from coming to the aid of their U.S. and Iraqi allies for nearly a week during the battle for Basra this year, The Times of London reported.

Four thousand British troops – including elements of the Special Air Services and an entire mechanized brigade – watched from the sidelines for six days because of an “accommodation” with the Iranian-backed group, according to American and Iraqi officers who took part in the assault.

U.S. Marines and soldiers had to be rushed in to fill the void, fighting bitter street battles and facing mortar fire, rockets and roadside bombs with their Iraqi counterparts.

Hundreds of militiamen were killed or arrested in the fighting. About 60 Iraqis were killed or injured. One US Marine died and seven were wounded.

US advisers who accompanied the Iraqi forces into the fight were shocked to learn of the accommodation made last summer by British Intelligence and elements of al-Mahdi Army, the militia loyal to Moqtada al-Sadr, the radical Shia Muslim cleric.

The deal, which aimed to encourage the Shia movement back into the political process and marginalize extremist factions, has dealt a huge blow to Britain’s reputation in Iraq.

Under its terms, no British soldier could enter Basra without the permission of Des Browne, the Defense Secretary. By the time he gave his approval, most of the fighting was over and the damage to Britain’s reputation had already been done.

Senior British defense sources told The Times that Nouri al-Maliki, the Iraqi Prime Minister, who ordered the assault, and high-ranking U.S. military officers had become disillusioned with the British as a result of their failure to act. Another confirmed that the deal, negotiated by British Intelligence, had been a costly mistake.

The Ministry of Defence has never confirmed that there was a deal with al-Mahdi Army, but one official denied that the delay in sending in troops was because of the arrangement agreed with the Shia militia.

A spokesman for the MoD said that the reason why troops were not sent immediately into Basra was because there was “no structure in place” in the city for units to go back in to start mentoring the Iraqi troops.

Colonel Imad, who heads the 2nd Battalion, 1st Brigade, 1st Iraqi Army Division, the most experienced division, commanded one of the quick-reaction battalions summoned to assist British-trained local forces, who faltered from the outset because of inexperience and lack of support.

He said: “Without the support of the Americans we would not have accomplished the mission because the British Forces had done nothing there.

“I do not trust the British Forces. They did not want to lose any soldiers for the mission.”

Lieutenant-Colonel Chuck Western, a senior US Marine advising the Iraqi Army, told The Times: “I was not happy. Everybody just assumed that because this deal was cut nobody was going in. Cutting a deal with the bad guys is generally not a good idea.”

He emphasised, however, that he was not being critical of the British military, which he described as first-rate.

A senior British defense source agreed that the battle for Basra had been damaging to Britain’s reputation in Iraq. “Maliki, and the Americans, felt the British were morally impugned by the deal they had reached with the militia. The British were accused of trying to find the line of least resistance in dealing with the Shia militia,” said the source.

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