British soldiers have been accused of executing up to 20 Iraqi prisoners in cold blood, a charge denied by the government.

The allegations were made by men taken captive after a battle near the town of Majat-al-Kabir in southern Iraq in May 2004, and also suggest that prisoners were tortured and mutilated.

An investigation by the Army and the International Red Cross could find no proof but human rights lawyers now demand that the case be handed over to Scotland Yard, the Daily Telegraph reported

Lawyers for five Iraqis claimed that they had detailed witness statements, photographs of corpses and death certificates of the men who died.

The charges, which have been strongly denied by the Ministry of Defence, are among the most serious leveled against British soldiers in Iraq.

Phil Shiner, a leading solicitor, said of the dossier: "We would be very surprised if it did not shock the nation."

The claims form the basis for a BBC Panorama programme due to be broadcast next week that has been condemned by the armed forces minister and senior Army commanders, who are convinced that the allegations are without foundation.

A spokesman for the Ministry of Defence said: "Allegations of mistreatment, unlawful killing and mutilations by British troops following an incident at vehicle checkpoint

Danny Boy were thoroughly investigated by the RMP. They found no evidence to support these allegations."