It is no surprise that Bono and Bob Geldof, the two leading celebrity philanthropists of our time, are both Irish. The Ireland into which they were born in the 1960s was caught between third and first worlds, and so was more likely to sympathise with the wretched of the earth than were the natives of Hampstead. As a devoutly Christian nation, it also had a long missionary tradition. Black babies were a familiar object of charity in Ireland long before Hollywood movie stars began snapping them up. Bono himself was a member of a prayer group in the 1970s, before he stumbled on leather trousers and wrap-around shades. Scattered across the globe by hunger and turmoil at home, the Irish have long been a cosmopolitan people, far less parochial than their former proprietors. Small nations cannot afford the insularity of the great.

Besides, if you were born into this remote margin of Europe and yearned for the limelight, it helped to have an eye-catching cause and a mania for self-promotion. Rather as the Irish in general were forced by internal circumstance to become an international people, so men like Bono and Geldof could use their nationality to leap on to the world stage.

Bono belongs to the new, cool, post-political Ireland; but by turning back to the old, hungry, strife-torn nation, now rebaptised as Africa, he could bridge the gap between the two. Even so, he has not been greatly honoured in his own notoriously begrudging country, or elsewhere. Harry Browne recounts the (perhaps apocryphal) tale of the singer standing on stage clapping while declaring: "Every time I clap my hands, a child dies." "Then stop fucking doing it!" yelled a voice from the crowd.

Paul David Hewson's rise to fame also coincides with the postmodern decline of politics into spectacle. What more suitable politician than a rock star in an age of manufactured sentiments and manipulated images? Having strayed in from showbusiness, Bono can present himself as outside the political arena, speaking simply from the heart; but his fame as a musician also means that he has a constituency of millions, which means in turn that the political establishment are eager to have him on the inside. For all his carefully crafted self-irony (how ridiculous for me, an overpaid rock star from working-class Dublin, to be saving the world!), the inside is a place he has never betrayed any great reluctance to occupy. Since an outsider is unlikely to know much about global economics, he is likely to take his cue from the conventional wisdom of the insiders, which is why Bono is both maverick and conservative.

One result of his campaigning has been a kind of starvation chic. In this impressively well-researched polemic, Browne recounts how Ali Hewson, Bono's wife, praised the work of her company's Paris-based clothes designer for being influenced by dusty African landscapes. She admired "the way some of the clothes look like they've been worn before and sort of restitched … to incorporate the continent, in a sense". Hewson's Messianic husband, or "the little twat with the big heart", as Viz magazine once dubbed him, has been trying to incorporate Africa into his image for a good few decades now. Like Geldof, he inherited the social conscience of the 1960s without its political radicalism, which is why he has proved so convenient a front man for the neo-liberals.

In fact, as Browne points out, he has cosied up to racists such as Jesse Helms, whitewashed architects of the Iraqi adventure such as Tony Blair and Paul Wolfowitz, and discovered a soulmate in the shock-doctrine economist Jeffrey Sachs. He has also brownnosed the Queen, sucked up to the Israelis, grovelled at the feet of corporate bullies and allied himself with rightwing anti-condom US evangelicals in Africa. The man who seems to flash a peace sign every four seconds apparently has no problem with the sponsorship of the arms corporation BAE. His consistent mistake has been to regard these powers as essentially benign, and to see no fundamental conflict of interests between their own priorities and the needs of the poor. They just need to be sweet-talked by a charmingly bestubbled Celt. Though he has undoubtedly done some good in the world, as this book readily acknowledges, a fair bit of it has been as much pro-Bono as pro bono republico.

If Bono really knew the history of his own people, he would be aware that the Great Irish Famine of the 1840s was not the result of a food shortage. Famines rarely are. There were plenty of crops in the country, but they had to be exported to pay the landlords' rents. There was also enough food in Britain at the time to feed Ireland several times over. What turned a crisis into a catastrophe was the free market doctrine for which the U2 front man is so ardent an apologist. Widespread hunger is the result of predatory social systems, a fact that Bono's depoliticising language of humanitarianism serves to conceal.

Browne's case is simple but devastating. As a multimillionaire investor, world-class tax avoider, pal of Bush and Blair and crony of the bankers and neo-cons, Bono has lent credence to the global forces that wreak much of the havoc he is eager to mop up. His technocratic, west-centred, corporation-friendly campaigns have driven him into one false solution, unsavoury alliance and embarrassing debacle after another. The poor for him, Browne claims, exist largely as objects of the west's charity. They are not seen as capable of the kind of militant mobilisation that might threaten western interests.

Bertolt Brecht tells the tale of a king in the East who was pained by all the suffering in the world. So he called his wise men together and asked them to inquire into its cause. The wise men duly looked into the matter, and returned with the news that the cause of the world's suffering was the king.

• Terry Eagleton's Across the Pond: An Englishman's View of America is published by Norton.