As war raged in Lebanon in the summer of 2006, people around the world called for international intervention to stop the shelling of civilians. In January this year, millions shared similar feelings of horror and anger witnessing the bloodshed in Gaza. Both events were especially painful to Muslims watching other defenceless Muslims being killed. But why have the deaths of vastly more unarmed Muslims in Darfur caused so little concern among co-religionists?

The Khartoum regime, brought to power in a highly ideological and fundamentalist Islamist coup 20 years ago, has killed an estimated 400,000 of its fellow Muslim citizens. Yet, there is near silence about massive human rights abuses in the remote western corner of Sudan. As Tareq Al-Hamed, editor of the Asharq Alaswat paper, has asked, "Are the people of Darfur not Muslims as well?"

When the International Criminal Court issued an arrest warrant for the Sudanese leader, President Bashir, in March, Muslim politicians from Senegal to Malaysia rallied behind him. The same people who demand international justice for war crimes in Lebanon and Gaza abruptly changed their tune. Instead of denouncing Bashir as the architect of ethnic cleansing, they congratulated him for defying the "conspiracy" to undermine Sudan's sovereignty so the West can take its oil. The Iranian Parliamentary Speaker, Ali Larijani, said the ICC warrant was "an insult to the Muslim world".

Mercifully, the views expressed by Arab and Muslim leaders are at odds with their citizens. The Lebanese American pollster James Zogby found 80 per cent of those questioned in four Arab countries were concerned about Darfur and felt it should have more media attention. However, they were reluctant to apportion blame, and, not surprisingly, they were hostile to international intervention. Meanwhile some commentators in Muslim-majority countries are questioning their leaders' support for Bashir.

According to The Daily Star of Lebanon, "Bashir has sought to cultivate an image of himself as an Arab/African hero who is standing up for his fellow Arabs/Africans by defying the edicts of foreign 'imperial' powers."

So, are Darfuris the "wrong" kind of Muslims because they self-identify as black Africans rather than Arabs, despite widespread inter-marriage in Sudan? The Ugandan president, Yoweri Museveni, cites Arab chauvinism against Africans. I have lived in Arab countries and seen first hand the racism and bigotry that commands the minds of the Arab political class.

The Canadian academic Salim Mansur claims: "Blacks are viewed by Arabs as racially inferior, and Arab violence against blacks has a long, turbulent record."

For the Nobel Prize winning novelist Wole Soyinka, the unwillingness to confront Arab racism is rooted in the role of Arabs in the slave trade. "Arabs and Islam are guilty of the cultural and spiritual savaging of the Continent," he writes.

The Ethiopian academic Mekuria Bulcha estimates that Arab traders sold 17 million Africans to the Middle East and Asia between the sixth and twentieth centuries. Yet, there is an almost total reluctance on the part of Arab intellectuals to examine their central role in slavery, past or present. Any attempt to confront persistent Arab racism is shouted down by appeals to Arab/African solidarity against the neo-colonialist West, a sentiment that seldom moves beyond slogans.

Sheikh Saleh Al-Fawzan, a member of the senior council of Wahhabi clerics responsible for writing Saudi school text books, states: "Slavery is part of Islam. Slavery is part of jihad and jihad will remain as long as there is Islam. It has not been abolished."

Arab racism is familiar to African guest workers in countries like Libya and Egypt, enduring routine verbal and physical attack. Sudanese Arabs suffer from their own racial identity dilemma, viewed as black by their Egyptian neighbours to the north (Sudan is a corruption of the Egyptian word for black). I have heard the Arab Sudanese use the word for slave (abid) to the faces of their fellow citizens who self-identify as non-Arab. It is also known for Sudanese parents to tease their darker-skinned children, calling them slaves.

To be charitable, it seems that Muslim and Arab leaders wish Darfur would simply go away. Hence their enthusiasm for postponing Bashir's arrest warrant "to allow peace talks to work". Shortly after the ICC announcement, key members of the Khartoum regime attended an Arab League summit. They were confident the League would call for the cancellation of ICC jurisdiction in Darfur, conferred by the United Nations Security Council in 2005. The meeting failed to agree on anything stronger than the usual denunciations of Israel and America. Privately, Jordan, Egypt, and Saudi were urging Sudan to deal with the ICC through legal channels. The Sudanese also failed to get a solidarity summit in Khartoum. However, Bashir did enjoy a victory tour of countries where he was hailed rather than arrested.

Arab and Muslim leaders are by no means unique in failing to back up their words with action. Both the US and the UK until recently had leaders who frequently cited their Christian faith, yet did little to help Christians being persecuted in China, Nigeria, Eritrea, North Korea or Egypt.

However, "Muslim solidarity" matters for two reasons. The Khartoum dictatorship is sensitive to the opinion of Muslim and Arab leaders. A genuine peace deal will be more likely as a consequence of private pressure from Iran or Egypt rather than Canada or Sweden.

Muslims' amnesia about Darfur is also symptomatic of the malaise affecting the public face of a faith that lacks the confidence to engage in constructive debate or renewal. Until Muslims can be self-critical without being condemned as heretics, there will be atrophy where there should be vibrancy, and polarisation and extremism where there should be tolerance and inclusiveness. Darfur's tragedy is fast becoming an indelible stain on the collective name of Islam and Muslims.

Ed Husain is co-director of the Quilliam Foundation and author of The Islamist