The government's most senior lawyer and the head of the military police have been ordered to the high court tomorrow to explain why they have failed to release documents about the aftermath of a fierce gunfight in Iraq when British troops are accused of mutilating and murdering civilians.

Lawyers have complained that documents held by the military police have been disclosed late despite promises that they had been given all relevant information. Lord Justice Scott Baker, Mr Justice Silber and Mr Justice Sweeney were told police had released more documents to Ministry of Defence lawyers that day, including statements about the possible exhumation of one or more bodies. The judges ordered the Treasury solicitor Paul Jenkins, and Brigadier Eddie Forster-Knight, head of the Royal Military police (RMP), to explain what was going on.

Lord Justice Scott Baker said: "At the moment the court is left in a state of complete confusion as to where things have gone wrong and whether the fault lies with the Ministry of Defence, Treasury solicitors or somewhere in between."

Six Iraqis are seeking an inquiry into the allegations that 20 Iraqis were taken prisoner, interrogated and killed after a battle between British soldiers and insurgents in May 2004 at a road checkpoint near Majar-al-Kabir in Maysan province.

The MoD says all 20 died "on the battlefield" and their bodies were taken to camp Abu Naji, a British base, to see if a leading insurgent was among the dead.