The fact that economist Noreena Hertz is extremely attractive is the least interesting thing about her. So let us get it out of the way straight off.

At 35, with a winning manner and a penchant for sharp dressing, Dr Hertz has attracted the kind of slathering press attention that has culminated in her being labelled "the Nigella Lawson of economics". The sobriquet is particularly outlandish given that Noreena is a svelte, Julie Delpy-esque blonde whose girlishness is a million miles away from Ms Lawson's magnificent cartoon womanliness.

The "dolly bird" coverage clearly bemuses Hertz. Yet she is canny enough to realise that with telegenic appeal comes huge opportunity. "If what it takes for issues that are literally issues of life and death to get coverage is for me to be this glam pastiche of a person," she reasons, "well so be it."

These issues of life and death involve the many inequities spawned by globalisation. Her first book, The Silent Takeover, a critique of multinational corporations, was an international bestseller, transforming its author into the UK's anti-globalisation poster-don: "Britain's Naomi Klein" when she wasn't being economics' Ms Lawson. Her latest, I.O.U.: The Debt Threat and Why We Must Defuse It, is a trenchant study of Third World debt: how it happened, whom it hurts, and how this beleaguered portion of the globe may end up biting the hand that refuses to feed it.

For Hertz's work is more than liberal breast-beating -it endeavours to be a psychology of debt. The reader is invited to imagine a situation in which their own bank manager behaves with the capriciousness of a First World lender. This lacing of macro with micro is central to her scheme of alerting her readership to its collective complicity with, and complacency about, this most pernicious economic relationship. Throughout, a problem that is perceived as vast and intractable is broken down into practical, actionable units.

And if accounts of the use of loans to secure arms deals and bankroll corrupt regimes are insufficient to rouse her readers' interest, then The Debt Threat comes with a sting in the tail. Without ever falling into the pat illiberalisms that the West brought 9/11 and its aftermath on itself, Hertz discusses the ways in which terrorism, disease and ecological meltdown may be the consequences of Third World stagnation. It is a future familiar from the more apocalyptic reaches of popular cinema: drought, famine, war, a situation in which "those who survive will find sustenance in their rage".

Here Hertz's measured tones give way to incredulity: "How stupid are we, allowing the world's poorest countries not to be able to provide schools or health systems so that extremist organisations provide them in their stead as they're doing all over Asia and Africa? How stupid are we in a world where everyone has access to television and can see the differences?" She will never forget the words said to her by the brother of the late Nigerian activist Ken Saro-Wiwa: "And then we got television. And we saw that other people had fancy apartments and drove expensive cars. And then we got angry."

Hertz is the queen of the killer statistic, dropping figures the way lesser individuals drop names. (Her only reticence in this area concerns the details of her book deal, but it is said that her last publication earned a six-figure advance.) However, she also appreciates that she must sugar the pill with narrative interest. There are tales of Western-sponsored outrages such as the Philippines' exorbitant, mercifully non-operative, Bataan Nuclear Power Plant, built along earthquake fault lines at the foot of a volcano; tales that would be amusing were they not so appalling. The opening chapter fair thumps along -an account of the 30 journeys made by the rock singer Bono back and forth across the Atlantic in pursuit of millennial debt cancellation, featuring an unlikely cast of characters: Billy Graham, an assortment of Kennedys, a lachrymose Jesse Helms and a resplendently foul-mouthed Saint (Bob Geldof). She is not above a few racy colloquialisms of her own, or the odd breathless passage. Anything to serve the message that capitalism needs to get its house in order, and fast.

Hertz should know. Fresh out of a Wharton MBA at the age of 23, she played a part in setting up the Russian stock exchange, going on to work for the World Bank advising the Russian Government on its privatisation programmes.

"Very quickly I realised that what we were doing was completely misguided and going to impact really negatively on millions of people. I left the World Bank a few months later extremely disillusioned." The period became the subject of, and inspiration for, her Cambridge PhD. "I realised that economics is not about models, graphs and curves, but about people, politics and society, about history and culture; that these are all legitimate things to be concerned about as an economist. In fact, you would be a much better economist if you did understand these things." She is grateful for her time on the other side of the debate. "Accepting the party line for even a brief period makes me extra vigilant."

Her conversion never conformed to so reductive a formula as poacher-turned-gamekeeper. "I have never described myself as an anti-capitalist. I am merely anti runaway-train capitalism." The capitalist, feminist and, indeed, style role model in her life came in the form of her mother: fashion designer and activist Leah Hertz. "I had a fantastic mother," says Hertz, suddenly young. "A cross between Mother Teresa, Superwoman and Cher." Leah died of cancer when Noreena was 20. She had brought her elder daughter up to be unashamedly precocious: school at 3, A levels at 16, degree from UCL under her belt by 19. Her current post is that of CIBAM Distinguished Fellow at the University of Cambridge.

Perhaps it is her mother's dynamic legacy that lends her such undonnish pragmatism. The Debt Threat closes not on a cloud of idealism, but with a practical blueprint -the Hertz route forward, if you will. First, illegitimate debts -the definition of which, she concedes, is open to debate -should be cancelled. Second, National Regeneration Trusts, or "islands of good governance", should be established in which non-governmental nationals and UN representatives decide how monies reclaimed should be spent. Finally, there should be a series of exacting new principles for borrowers and lenders.

Equally importantly, Hertz is asking her readership to take responsibility for a situation too often seen as beyond the influence of individuals without Bono's rock-star credentials. Each edition of the book will contain a postcard addressed to the Prime Minister, demanding that he make headway on debt in his capacity as chair of July's G8 summit. In the run-up to British and American elections, and with Britain to be head of the EU, Hertz is evangelical about the potential for people power. "We have a real opportunity in the coming months to draw the lines along which the battle will be fought. You don't have to buy my book, but write your postcard.

Talk about these issues when you're picking up your kids from school, at the hairdressers', at a dinner party. Read economics books in your book group. Start questioning the world we live in and making it clear to politicians that we demand a stake in a better one."

There is a rich vein of bourgeois idealism in this, but then idealism is no bad thing in a culture in which more young people voted in the first Pop Idol final than in that year's general election. "I'm an optimist," admits Hertz. "Nobody can do everything, but everybody can do something. Together we can change the world."

When she is not teaching, delivering public lectures, protesting, writing advisory documents for Number 10, or telly donning here and in the US, Hertz unwinds in her North London home "in the company of Tony Soprano or Jack Bauer", or among the tribe of friends cited in the acknowledgements to her book. One gets the impression that she would make rather a nice friend, with her gentleness, ready laughter and intellectual bravura. I note, as I leave, that she has tiny petal transfers decorating her toenails, where once such an ideologue might have had flowers in her hair. It is the one concession to flakiness she allows herself.

To buy IOU by Noreena Hertz click here