According to the principle of ubuntu, strangers are always welcome in the new Republic of South Africa. Nelson Mandela explicitly espoused the idea, but his country's civic leaders are now wondering what happened to it. Small wonder. The upsurge of xenophobic violence in and around Johannesburg in the past week has paralysed commercial districts, driven thousands of immigrant workers from their shacks and claimed at least 22 lives, among them that of a homeless man burned alive in his blankets.

Harrowing images of the (still unidentified) burning man recall the nadir of the apartheid era, when black-on-black violence terrorised the townships and suspected collaborators were set alight with petrol-filled tyres. A return to such brutality is shocking by any standards. Yet it is also remarkable that South Africa's truce with its great influx of foreigners has lasted so long. The country has managed to absorb up to five million economic migrants even as President Mbeki's administration has left 40 per cent of South Africans worse off than they were under apartheid. Crime is endemic, with 50 murders a day in Johannesburg alone. Education, for most, remains rudimentary at best. Mr Mbeki has personally deepened the human and economic toll of the Aids pandemic by refusing to acknowledge its extent or talk frankly about its causes, and he has stubbornly refused to face reality in Zimbabwe.

By failing to condemn Robert Mugabe's murderous dictatorship, Mr Mbeki has done more than any other outsider to keep him in power. He has also perpetuated the flood of Zimbabwean refugees who now comprise three fifths of South Africa's foreigners. They seek shelter and livelihoods in an economy burdened further by systemic corruption and sharply rising food prices. The results include lynchings and looting that have left one Johannesburg district looking “like a war zone”. For Mr Mbeki to announce the creation of panel to study the causes of the lawlessness, as he has, is fiddling while Rome burns.

In the twilight of his power, Mr Mbeki has shown himself almost as detached from reality as Mr Mugabe. He can claim some credit for presiding over robust economic growth of about 5 per cent per year. Yet he has failed spectacularly to channel its proceeds to the townships where xenophobia now threatens to take root. Even the state-backed low-cost housing programmes that have helped to lift a lucky minority out of poverty now appear part of the problem, not the solution: attacks on foreigners accused of gaining access to new homes at the expense of native South Africans may have triggered the current violence.

Immigrants from as far away as Somalia are now vulnerable, but it is Zimbabwe's crisis that has turned simmering resentment into rioting. Zimbabwe should be booming thanks to soaring world cereal and commodity prices. Instead, it is acting as a brake on the entire regional economy and flooding South Africa with workers willing to accept a fraction of average local wages. Mr Mbeki could still reverse much of the damage by abandoning Mr Mugabe, insisting on full international access to polling stations for Zimbabwe's second-round presidential vote and ending his puerile sabotage of British efforts to isolate Mr Mugabe at the UN. His record inspires little confidence, but at least the effects of his complacency are now in plain view on his own streets.