On average 20 Iraqis and two coalition soldiers have died every day this month.

The attack came as political leaders continued to haggle over the formation of a new government. Iraq's new police and army units, instead of taking responsibility for imposing law and order, are abandoning patrols or taking refuge in their guardhouses when challenged.

On the Syrian border, US troops in the Sunni city of Husaybah report mass desertions. An Iraqi unit that had once grown to 400 troops now numbers a few dozen who are "holed up" inside a local phosphate plant.

Major John Reed, of the 2nd Marine Regiment, said: "They will claim that they are ready to come back and fight but there are no more than 30 of them on duty on any given day and they are completely ineffective."

In Mosul, which has been a hotspot since insurgents fleeing Fallujah effectively overran it last year, residents have complained to newspapers that police now rarely patrol and only appear in response to attacks.

But greatest concern has focused on Madain, the town 14 miles south of Baghdad that in the past few weeks has been at the centre of the biggest crisis amid conflicting claims of ethnic cleansing.

Residents say that since a series of tit-for-tat kidnappings began three months ago police have effectively abandoned the town.

Sunni and Shia communities say two to three people have been disappearing each day since, blaming either elements of the Shia Badr Brigade and Sunni Ba'athists for the kidnappings.

When a convoy of police did try to install order, insurgents ambushed them. Those who survived were burnt to death.

The full extent of the lawlessness was confirmed last week when it was announced that 58 bodies of both sexes and all ages had been discovered in the Tigris between Feb 27 and April 20.

Both Shia and Sunni political groups have claimed that their communities are included in the dead. Police have failed to provide an explanation for their murders.

The failure of the victors of January's election to form a government has resulted in the defence and interior ministries being placed in limbo, and security experts cite this as partly responsible for the subsequent fall in army and police morale.

Ministerial initiatives against insurgents have all but ceased, many senior officials are due for replacement and recruitment has been hampered by confusion over future selection policies.