According to the environmental journalist Lucy Siegle, most women now buy half their bodyweight annually in clothes. The writer's new book, To Die For: Is Fashion Wearing Out the World? (£12.99, Fourth Estate), states that the average female invests in 62lb of clothing each year, has upwards of 20 garments hanging in her wardrobe that she has never worn and owns four times the amount today than she did in 1980.

When a story written by Siegle for the Daily Mail to publicise the book was published at the end of last month, and then featured on the newspaper's website, it was met if not quite with howls of derision, then with a healthy dose of scepticism. Perhaps she's touched a nerve.

Siegle's figures are based on research conducted at Cambridge University into textile imports as opposed to sales, it was argued, and the two do not necessarily tally. It's safe to say, though, that any half-viable manufacturer is unlikely to over-estimate their fabric requirements on a grand scale – that is, throw away large amounts of investment – and stay in business for very long.

Equally contentious appeared to be the fact that women weigh approximately 124lb (8st 12lb) in the first place. Given that we are consistently informed that most of us are sized somewhere between a UK 14 and 16 this seems on the light side. The loaded nature of issues concerning both bodyweight and wardrobe expenditure make it far from surprising that this, in particular, saw eyebrows raised. Still, it's just an evocative gimmick, surely, and the principle behind it – that is, we buy a huge amount of clothing – holds water.

With this in mind, there's more. Women are expected to spend £133,640 in a lifetime on fashion. In 2007, three pairs of jeans were sold each second. Between 2001 and 2005, while spending on womenswear rose by 21 per cent, the price of individual items dropped by 14 per cent. And so forth.

Such facts and figures, for all Siegle's diligence – which is considerable – are unlikely to be wholly representative: statistics are statistics and the way in which we choose to digest them is clearly subjective. Having said that, we only have to look around us to see that there are more clothes and accessories available to buy both on the high street and in more upscale shopping destinations than ever. And we only have to observe the shopping patterns of colleagues, friends and family to know that, to varying degrees, we must be doing our bit to consume them. That much is clear.

But why?

For her part, Siegle is most vocal in the first place about the culture of celebrity endorsement. Until very recently, she claims, we were only interested in what celebrities wore on the red carpet or to a film premiere. Now, though, we are obsessed with their off-duty wardrobes too.

That is also true but celebrity endorsement has been around since the court of Marie Antoinette, the difference today is that far more of us can actually afford to emulate our idols, or we think we can at least – our bankers, struggling with burgeoning debt, might beg to differ. Where we used to look on in spellbound wonder at Marlene Dietrich's Dior gown at the Oscars, say, or Grace Kelly's Hermès bag, and even at Madonna's Jean Paul Gaultier conical bra, we would never have expected, or even necessarily wanted, to own them.

Until the turn of the 21st century this was a purely aspirational and entertaining activity, the stuff of dreams and/or nightmares depending on how we chose to look at it. Now, though, with budget copies of any outfit worn by even the least interesting young hopeful proliferating and images of the same published everywhere from online to the pages of newspapers and magazines, far more of us believe we can actually live that dream.

The rise and rise of Asos.com is a case in point. It may have cast off its original tag – As Seen On Screen – and have an eye on a more credible and far-reaching position in the market but the premise the business was originally founded on remains the same.

More significantly, Asos, like all other online shopping destinations, allows us to purchase clothing at the mere click of a button, making poring over a garment in a store, returning on two or even three separate occasions to consider just how much we want or need it redundant. Neither do we save up for clothing the way previous generations did, appreciating them far more just for that. Shopping for clothes is now a practice as undiscerning as many of the products we shop for. And that is regrettable.

Blame the so-called democratisation of fashion if you will. Images straight from the catwalk – and the inevitable fast-fashion copies that go with them – are also everywhere. Formerly, the designer fashion industry was a closely regulated concern – as late as the mid-1990s, all photographers at the international collections were accredited journalists required to sign forms limiting the use of any images to prevent plagiarism.

And if, since the mid-20th century, the world's leading couturiers, including Christian Dior and Coco Chanel, might have been persuaded to sell their patterns to American department stores, any buyers paid good money for them and their execution and distribution was closely guarded with a view to protecting exclusivity. Today, the shows are an all-singing, all-dancing, all-blogging, all-tweeting media circus. And consumers can "get the Marc Jacobs look" or whatever, only hours after the designer's biannual New York show has taken place, and this despite the fact that the prototype, which is high-end and therefore takes longer to produce and is necessarily more expensive, won't go on sale until almost half a year later.

The new Prada shoe, the make-up at Balenciaga, the tights at Chanel, are common knowledge before the first designer outfit has even made it on to the runway. And where such material used to be seen as news – admittedly not necessarily hard news, but news nonetheless – the purpose of which was to show people what they might, or might not, like to wear six months down the line, it now fuels a consumer habit that might be described as full-blown addiction.

The effect of this has been huge across the board. If we accept that it is now almost impossible for designers to copyright their ideas – and much has been written about the time and money involved in tracking down and removing everything from catwalk-inspired pieces deemed too close for comfort to blatant counterfeiting – then they are forced to take action in other ways. And so they have.

We may not have the budget to pay for a straight-off-the-runway, so-called seasonal statement piece, but we can and do buy designer sunglasses, bags, hosiery, shoes or even just an itsy-bitsy keyring/mobile-phone trinket to go with them. And just as the high street famously turns over clothing at breakneck speed with new drops appearing in any self-respecting fashion store on a weekly basis, so designers too have upped the ante with the aforementioned small-accessories market booming and pre-collections, cruise collections, all-year-round classic collections, multiple diffusion lines and more freshening up of the formerly proud-to-be-impenetrable designer stores.

With this in mind, where it was once not uncommon for fashion's biggest names to force consumers to knock at a locked door to gain access to their hallowed portals "by appointment only," today anyone and everyone is welcome at the vast majority of even the most elitist retail outlets where they will be greeted, if not quite with open arms – some things never change – then certainly without having to break in.

At the same time, and to establish a point of difference, fashion's big names are ensuring that their main line collections are more complex and therefore more difficult to interpret. And that is reflected in their price. The customer who is prepared to spend a three or even four-figure sum on her so-called seasonal statement piece does not want to show up at the party and find a half-dozen other women wearing the same.

The Independent regularly receives letters from readers decrying the price of clothing on the fashion pages, complaining, for example, that a dress might cost as much as £200. This is a dangerous mindset and, at the risk of attracting more disapproval, even a decade ago anyone working within the industry would have replied that £200, or indeed far more than that, is a fair price for a garment if it came from a great creator heading up a French or Italian fashion house and was made the country of origin by highly trained craftspeople all of whom were thereby respectably and respectfully employed.

In a similar vein, it was considered a mark of shame for a fashion editor to wear a copy of a catwalk design – we were, effectively, biting the hand that fed us by so-doing. Neither would we have shown high-street clothes mixed with designer looks on our pages or, certainly, demonstrated to people just how they might emulate them for a lower price. Cheap was cheap. Chic was chic. And the two worlds should never knowingly collide.

The basically protestant British mindset decrees that a desire for fashion is rooted in vanity and therefore to be frowned upon. But is it really any more shameful to want to dress in clothing that is interesting and well made than it is to lust after a precious first edition of a much-loved book or to buy a beautiful car?

At best, fashion is an entirely valid vehicle via which to express ourselves and one that can be passed down through generations of women carrying with it as much emotional power as a grandmother's wedding ring or a mother's scented cotton lawn handkerchief. Somehow, though, society has developed in a manner that deems it acceptable for us to descend en masse upon a low-budget store from where we emerge with bagfuls of clothes that we will either wear infrequently or not at all.

The hypocrisy – and indeed outright snobbery – that drives our disapproval of a Wag shopping on Bond Street for more of the same, meanwhile, only their carrier bags are glossy, carry more expensive merchandise and spill over with clouds of tissue paper, is disingenuous in the extreme. Contrary to popular mythology, shopping in the modern world has little to do with budget. It is not the less well off who have caused the boom in cheap fashion but the middle classes in search of a sartorial bargain. Neither are the super rich responsible for the proliferation of exorbitantly priced product. Instead, and as always, supply reflects demand. We choose to buy more low-priced fashion – and just more fashion – now than we used to. And that is more suspect.

"How do they make them so cheap?" It could be Lorraine Kelly's mantra. But, of course, someone somewhere in the world is always going to pay the price. Although there is no guarantee that all designer clothing is made in the best possible conditions, luxury brands that do employ cheap labour are likely to have longer lead times and bigger budgets than their mass market, high-street counterparts. Similarly, it would be naive to claim that price invariably reflects quality but more high-end clothing does generally come with a degree of care attached because those behind it can afford it.

And so, in France, artisans really do tend to make the clothes. In Italy, pioneers of the ready-to-wear industry and the computer technology that goes with it have passed down their knowledge since the 1950s and their expertise is second to none. Should we live in a world where the concept of investment in clothing expires then technicians such as these will die out and innovation and creativity will ultimately suffer for that.

To say that all budget clothing comprises cheap copies of what we see on the catwalk would be to over-simplify the matter. The high street, we all know, has come of age. Topshop sponsors many of Britain's youngest and most vulnerable designers. It also has its own design team which, while informed by designer fashion, is by no means reliant on it. Ditto the aforementioned Asos. However, a huge amount of the fashion we are buying is derivative, brazenly upheld in the press as a low-budget alternative to the real thing. Blame the word "commercial", perhaps, which in itself is misleading. Sell 10 jackets for £1,000 or 100 for £10 and the end result is equally cost effective to the designer or manufacturer, after all.

Of course it's a good thing that fashion is today available to many as opposed to merely the privileged few and Miuccia Prada, to name just one hugely influential name, has probably done as much for our collective fashion consciousness both in this country and overseas as Sir Terence Conran has for the look of our homes

So what's the answer? Buy carefully and buy less, is Siegle's argument and she's right. Consider everything from the origins of any garment, its sustainability and the working practices that went into its creation to whether it will actually add to the quality of your life or not. It almost goes without saying that, if we all chose to do that, the amount of product would naturally diminish to more manageable proportions. It may become more expensive as a result but the planet will only benefit for that.