Sophie Kinsella knows her labels. As the author on whose books the glitzy new movie Confessions of A Shopaholic is based, it is fitting that she is decked out in designer gear.

Sitting in a London hotel, she gives me a rundown of the outfit she's wearing. Jacket: soft, black leather, by German label Rutzou; shirt: patterned chiffon, by LK Bennett; trousers: black, skinny, by Paul Smith; shoes: open-toed, dove grey and teal suede by Miu Miu.

Bag, ah yes, by Prada. The large, pale leather holdall, embellished with inky swirls and a drawing of a pretty fairy, sits by her side in London's Dorchester Hotel like a small obedient child. "We were filming scenes for Confessions in Miami," she explains, "And I bought this when we were on set in the Prada shop. I should have been concentrating on the action. Instead, my eyes were drifting to handbags! It's my souvenir. I love it."

A petite, pretty brunette, she looks younger than her 39 years. Yet she carries on her slim shoulders the responsibility of being the creative source of a movie that is being hailed as the natural progression from Sex And The City.

While the women in SATC were slightly unreal fashion plates, who never worried about where the money for the next pair of Jimmy Choos would come from, Confessions Of A Shopaholic seems more in touch with the average woman's relationship with shopping.

The unlikely heroine of both film and Sophie's series of Shopaholic books is Becky Bloomwood. Becky has never seen a shop she could walk by. "Especially in the book, she's not just buying high-end clothes; she's buying everything. She's buying moisturisers, she's buying rugs for her flat, she's buying lamps and make-up. It's about the shopping itself."

Even though Becky's desires are relayed with great humour in the books -- and by Isla Fisher, who plays her in the movie -- there is an underlying point being made about our obsession with consumerism.

Call it mall-aria or affluenza, shopping has become as much of an addiction as a hobby for many young women. It is not about needing things, it's about satiating a desire that gets bigger and bigger the more you feed it. So, in The Secret Dreamworld Of A Shopaholic -- the first book of Kinsella's series of five -- Becky's wardrobe is stuffed with unworn 'bargains', still with their labels attached.

In the film, the matter is touched on more lightly; one might say, more flippantly. Trying to squeeze all her excess purchases into her closet, Becky uses those vacuum-packed bags you might see advertised late at night on TV shopping channels. Her flatmate, Suze, accidentally sets them loose, and clothes explode all over the hapless pair.

It's a fun moment of physical comedy and Kinsella defends it as such. "Ultimately, it's entertainment," she says. "I've never wanted to bang anyone over the head with a message. I've just wanted to tell a good story.

"But then I think a good story actually works better if it's grounded in reality, however lightly it is. There is a balance you strike between telling a funny story which people enjoy and actually having something to say about consumer culture and the world and human nature."

The funny thing is that Kinsella is probably more successful than many other, more heavy-handed commentators have been in getting a point across about the consequences of our shopping culture. For one thing, her readers -- 15 million of them in 35 countries -- are largely young women.

What they read is that Becky is only in her 20s, but she's on the verge of personal bankruptcy. Financial experts have been warning about personal debt for the past few years, and in Ireland we find ourselves with some of the highest levels of credit-card debt in Europe. She could so easily be any of us.

The first Shopaholic book was published more than eight years ago.

"Now that it's out on screen, when the economy is on everyone's lips, it's incredibly timely," admits Kinsella. "And it's certainly also about the banks, it's about the financial institutions on the one hand saying, 'Here's an overdraft, you clever girl, why don't you take out a loan,' and the next day sending her a letter demanding repayment. It's a gentle dig at the hypocrisy of those institutions which have become more and more of an issue.

"Until she reaches the wall, she doesn't realise how far she's gone. As we don't. Because the bank keeps offering her credit. At one stage, she thinks, 'Well, I must be able to afford it, because the bank keeps offering it.' There's a kind of trust there that they know better about these things than you do."

And for all that she loves nicely made clothes and shoes, Kinsella has a problem with the dictates that women's magazines issue to their readers. "Have you noticed that thing they do?" she asks, "The 'must-have' thing? It's not the 'Maybe you'd like this', it's all 'Must Have! Must Have! Must Have!' The imperative flog.

"And you know in your head that this is total bullsh*t. Even so, you're still, 'Really? I should get that.'"

Not that Kinsella lets women abdicate responsibility for their own woes. "Most of us are a bit of a mish-mash. On the one hand, we can be responsible, on the other hand, a bit crazy, we know what we should be doing, but we can't help ourselves," she says.

Kinsella is her own best example. She's no Becky Bloomwood these days -- she is married to the headmaster of a school in Hertfordshire, England, and has three young sons, Freddy, Hugo and Oscar. Even though hordes of teenage girls are descending on cinemas to soak up the considerable glamour in the Confessions film, Kinsella's boys were only interested in the cameras and the catering truck when she brought them on set with her.

She studied philosophy and economics in Oxford, is a classically trained musician, and was even a financial journalist for a time. Can she seriously be the woman who understands a girl's need to go shopping, even in the face of a large overdraft?

As it turns out, yes. You can't judge the book by the cover with Sophie Kinsella. For one thing, her real name is Madeleine Wickham -- Kinsella is her mother's maiden name, and she likes to think she picked up the Irish "storytelling gene". She had published a number of novels under her real name, but used the Kinsella pseudonym when she started writing the Shopaholic series -- which are in a much lighter tone -- so as not to confuse her original readers.

And Kinsella knows what it's like to live in a bit of a dreamworld. She recalls attending one boring press conference after another on pensions, or what not, for her reporter's job -- all the while fantasising about what shops she could nip into during her lunch break.

"I could scoot to Covent Garden and back in my lunchtime if I extended it by 10 minutes -- that's what I used to be thinking about!" she says. When she wrote the opening scene of her Shopaholic book, where Becky opens her Visa bill in horror, Kinsella channelled all the emotions she used to feel when she opened hers. "That sort of amnesia, you would open your bill and honestly not remember going into these places. It would mean nothing to me. 'Someone must have stolen my card!' That kind of thing."

Kinsella herself is almost easier to relate to than Becky Bloomwood. Becky is a comically bad shopaholic; Kinsella is more like your average girl, who went a bit nuts with her first few pay cheques, eventually got sense, but still occasionally splashes out. (Although she can probably afford it more than most of us thanks to her book sales and film options; she and hubby Henry recently installed a home cinema with surround sound in their basement).

She's not afraid to be a bit girly. In one YouTube video addressed to the legions of fans of her Shopaholic books, she generously gives them a tour of her shoe collection -- her shoe museum, or shoe-seum as she calls it.

Pride of place are a pair of cherry-red, peep-toe court shoes which she bought to wear to her son's christening. Another favourite are a pair of summery wedges adorned with a cheerful yellow flower: they were the only pair of shoes that she could comfortably wear thro-ughout her last pregnancy three years ago.

She loves material things, yes, but often her most prized possessions remind her of a happy moment in life. We should give ourselves a break is her message. For example, Becky is most definitely what Kinsella calls a "cautionary tale"; she has to sink very low before she realises she's in trouble. But it doesn't mean she's an idiot.

"She's very grounded, she cares about her family, she's very loyal to her friends. She is NOT a superficial person. She likes nice things, but she is actually a very moral person."

It's often the accusation levelled at young women today: that they are obsessed with themselves, that they only care about possessions, or men, or body image. Interestingly, Becky Bloomwood hardly ever mentions her weight, nor does she lie awake at night worrying about why she hasn't got a boyfriend. In that way, she's actually quite a positive role model.

"You know, I like shoes, but I also earn my own living," she says.

"I don't see why the two can't coexist. I think it's very depressing if people see someone who likes shoes or lipstick and assumes that they don't have a brain. Why can't we do both? I used to go to philosophy tutorials in a miniskirt and lipstick. Why not?

"I wouldn't take a woman less seriously because she looked nice. I would think, 'All power to you!' It's something to be fought against."

Just keep an eye on the bank balance, ladies.