Hold Iraq death probe, Blair told

The study, by US and Iraqi researchers, suggested the risk of violent death was higher after the war than before. UK ministers rejected October's Lancet figures, but have offered no alternative estimate of their own.

The letter's publication marks the launch of a new campaign by health charity Medact and the Iraq Body Count project.

Names on the letter include retired General Sir Hugh Beech, the Bishop of Coventry, and an ex-ambassador to Iraq.

The signatories urge the prime minister to set up an independent inquiry to establish just how many people have been killed or injured in Iraq along with reasons for the casualties.

Lord Garden told BBC Radio 4's Today programme: "We have taken it [Iraq] over and we are going to try and make it a democratic country.

"If we appear to be discarding the people there and saying they are not really important we are going to lose that battle."

The letter to Mr Blair says: "As you know, your government is obliged under international humanitarian law to protect the civilian population during military operations in Iraq, and you have consistently promised to do so.

"However, without counting the dead and injured, no-one can know whether Britain and its coalition partners are meeting these obligations."

The letter's publication marks the launch of a new campaign by health charity Medact and the Iraq Body Count project challenging the government to count casualties.