Iraqis often debate whether it is the Labour party as an institution or Tony Blair as an individual that is the real British culprit in their tragedy.

This issue needs to be addressed, not least for the future of relations between Iraq and Britain; but the debate echoes the deeply felt anger among Arabs and Muslims worldwide.

Blair's callousness about Iraqi lives and the country's ongoing destruction should now be notorious. In December 2004, the BBC's Andrew Marr asked Blair during a visit to Baghdad's Green Zone: "Many thousands of people have died for this moment, including scores of British people: are you sure that this prize was worth that price?"

Blair's answers ranged from, "I know that we are doing the right thing" to, "Yes, I believe we did the right thing" and, finally, "I've got no doubt at all that that is the right thing for us to do".

But all that was in the second year of the occupation, and some Iraqis naively thought that the Labour party would deal with an individual who discredited its ethical foreign policy. It proved a delusion. Blair was re-elected as prime minister.

"Why?" we asked, while witnessing the descent of Iraq into hell. Has Blair apologised for the death of 650,000 Iraqis? Of course not. His emotional resignation speech to members of his party two weeks ago displayed the same rhetoric: "I did what I thought was right for our country."

This is not unusual. History, the gatekeeper of collective memory, teaches us that dictators and tyrants never admit to committing crimes, but adamantly justify them by saying that they acted in the national interest.

Parties and ideologies often act in the same way. Parties rise to power on the strength of declared commitments, and they must be judged on whether they fulfil them.

It was the late foreign secretary, Robin Cook, who launched the Labour government's ethical foreign policy in April 1998, following Labour's manifesto of 1997 which pledged: "We will make the protection and promotion of human rights a central part of our foreign policy." I was one of many who believed that.

Since then the Labour government has been engaged in the invasion and occupation of Iraq, based on a lie, and a hypocritical policy on Palestine involving doing nothing about Israel's aggression against Lebanon. Neither policy can be described as ethical.

Robin Cook kept a measure of sincerity in his resignation speech in the House of Commons on the eve of the invasion of Iraq, by pointing out the hypocrisy regarding Iraq and Palestine.

But the Labour party continued its march under Blair, guided by a shared sense of mission and vision with President Bush in his war on terror, laced with rhetoric about "legal and moral obligations towards Iraqi people". How to dispose now of this legal and moral responsibility?

In the fifth year of occupation, Iraq is a country of horrors, invoking comparison in the mind of Iraqis with the barbarity of the Mongols in 1258. An academic, who fears for his life, told me last week that every aspect of human rights has been violated.

This April Iraq lost between 3,000 and 10,000 of its citizens, depending on who estimates the figures, since no one officially counts. British forces lost 12 soldiers, the largest monthly total in the 50 months of occupation. The United States lost 104 soldiers, with 634 injured.

No one has yet declared the number of dead and injured foreign mercenaries, euphemistically labelled "contractors", whose numbers in Iraq are widely believed to equal the official occupation troops.

The latest military operations and the much-publicised "surge" have displaced a further 27,000 Iraqis in three months.

The pretext of fighting the militias and murder squads was shown to be phoney by the continuing daily spectacle of handcuffed, tortured and brutally murdered men found after night curfew; by gruesome executions in public places by thugs wearing police uniforms; by the sectarian walls built around many districts in Baghdad and other cities; and by the corruption and oil-smuggling, which is breeding new militias for the political parties in government.

The United Nations last month confirmed a massacre on January 28 in the village of al-Zarka, in the province of Najaf, in which more than 260 people were killed by the police and by aerial bombardment from multinational forces.

The Labour party should not be relieved of its responsibility just because Blair is leaving. It is the moral responsibility of its members to question the party's role in the destruction of Iraq, and whether its new leader will listen to them and to the people of Iraq.

The overwhelming majority of Iraqis want the occupation forces out now, and they believe that the enemy is the occupation itself and not "al-Qaida and Iranian-backed elements", as Blair tells the world.

In order to put an end to the daily bloodshed and to build a lasting peace, the Labour party and its new leader must accept that this will only be possible when they acknowledge that there are different voices that represent the Iraqi people.

These include the widely popular resistance, whose different strands include both political and armed movements. And the British government must agree to initiate a compensation programme for the destruction it has helped to cause.