When Zadie Smith’s first novel came out five years ago the critics stampeded to their copies of Roget’s Thesaurus in search of sufficient words of praise. White Teeth was, they said, a joy to read. Masterly. Ambitious in scale. Reminiscent of Charles Dickens. No less a figure than Salman Rushdie described it as “an astonishingly assured debut”. She was hailed by fashionistas as the chronicler of hip, multi-cultural London.

Indeed, there seemed to be only one dissenting voice amid the avalanche of accolades. According to this literary sourpuss, the 24-year-old novelist’s account of life in multicultural London was the work of a precocious poseur. What’s more, it read as if the author were “a script editor for The Simpsons who had briefly joined a religious cult and then discovered Foucault”.

And who was the author of this wounding attack? It was Zadie Smith herself, who carried on the self-inflicted kicking by pronouncing the following verdict: “There are great swathes of stuff I really can’t bear to read.”

Such remarks are typical. Since being hailed as the most exciting young novelist of her generation (and certainly the one with the most striking looks),she has toyed with the ideas of modesty and humility and tested them to startling new experimental limits. Asked last week if her third and latest novel, On Beauty, would make the Booker shortlist, she was characteristically dismissive.

“No, there’s no chance,” she told an American interviewer. “Have you seen the f****** list? Any other year, maybe. But it’s a hell of a list.”

True to form, On Beauty slipped easily into the final six alongside works by two Booker veterans, Julian Barnes and Kazuo Ishiguro. What’s more, she made it in ahead of works by her old friend Rushdie, and previous winners Ian McEwan and JM Coetzee.

But unfortunately for Smith it wasn’t her Booker prospects that caught the public imagination last week. In that same interview, with New York magazine, she delivered what appeared to be a savage attack on England and the English.

“It’s a disgusting place,” she was quoted as saying. “It’s the way people look at each other on the train; just general stupidity, madness, vulgarity, stupid TV shows; aspirational arseholes, money everywhere.” Could this really be the same woman who has written so affectionately about Willesden and Cricklewood? Confronted about these remarks on Radio 4’s Woman’s Hour on Friday, she denied them and admitted she’d been “tearful” on reading the newspaper reports. “I didn’t say that,” she insisted. “And I’m incredibly embarrassed.” (Although she did concede that she’d been rude about trash television.) The truth is that Smith just isn’t good at being interviewed. “I have nothing to say,” she complained to one puzzled newspaper reporter. She always seems astonished at any show of interest in her work or personal opinions. “Why did you write about infidelity at the beginning of your marriage?” she was asked on Woman’s Hour, in a reference to On Beauty. “I don’t know,” she replied.

Interview aversion is an occupational hazard for writers. They sit in their spare rooms for two years, locked in combat with their typewriters or computers, before they emerge blinking into the sunlight. Then suddenly they are hailed, if they are lucky, as the most exciting innovation in literature since the discovery of the pronoun. That sort of success can turn a girl’s head.

It hasn’t yet turned Smith’s, although the public interest was so great after White Teeth that she fled terrified to the United States and threatened never to write again.

“She’s not at all grand,” says a friend. “She doesn’t puff herself up at all, unlike many literary types. Quite the reverse. In fact, she finds the whole thing rather baffling. And although her relatively humble background is important in her work, she’s not at all chippy.”

Reluctant or not, she has posed for the current issue of Vogue; although from the way she stares gloomily into the lens you’d think she was posing for the “before” shot in an advertisement for indigestion pills.

What really baffles Smith about all this is that she genuinely doesn’t think that much of her work. When Woman’s Hour turned to the subject of her writing, she said: “I don’t think I’m a hugely original writer.” It’s a point that some critics have also remarked on, including the Sunday Times fiction editor Peter Kemp.