Shopping can be such an elitist sport at times. If you're not prepared to play by the high street's - and the designers' - strict rules, finding garments to suit your body shape, budget and taste can turn into a purchasing endurance test.

For a start, there are the numerous sizing charts to get your head around. With numerical lists peculiar to Britain, Europe and the US all hanging around our high streets, as well as the usual small, medium and large, just finding something to theoretically fit can be problematic, even if you are a perfect size 12.

Every so often, the high street launches a new brand for "real women" - whatever that's supposed to mean. Yesterday was the turn of Lily Allen, who looked at the 300 dresses in her wardrobe for inspiration and wanted something more than the "usual pretty flower style".

She describes the results as a summer collection of "super-girly" clothes for women of all sizes.

"You know how I feel about fashion: it's for everyone, not just a load of super-skinny models," she says.

Despite her fine words, Allen is a long way from being a plus-size role model. Aside from Nigella Lawson, the search is still on for a glamorous icon. The average British lady measures a curvy size 16. There are thousands of women like Lawson being forced into the world of "plus size" fashion, where most catwalk designers dare not go. So what does fashion, and shopping, offer them?

Jacqui Kelly understands the problems of plus-size shopping.

A size 20 and fed up with the clothes on offer on the high street, she decided to set up her own range, Chesca, which is now stocked in John Lewis and House of Fraser stores. "I used to go out shopping with my friends and they would buy clothes in all the usual stores," she explains. "I would always come back with shoes or bags. The idea of dragging them up to the fourth floor of a department store just wasn't worth it."

Kelly, a professional buyer at the time, decided to create her own line of occasion wear that would specifically cater for the plus-size market. "Women buy things because they have an event to go to," offers Kelly. "Things like weddings and the races spring to mind. But we also do a smart trouser suit in winter and tops that you could wear with jeans out to the pub."

Stina Scott is a size 16 to 20, depending on the brand in question, and finds it increasingly difficult to locate clothes she likes. "There are times when I buy something just because it goes round me and it fits," says 54-year-old Scott. "So much of what you see in the shops doesn't fit properly or looks like something someone's elderly mother would wear. There's nothing particularly young and trendy that I'd wear."

Scott believes the problem lies with evening wear, which she says isn't often made any larger than a size 16. "I've got two functions to go to in the next few months and finding something to wear for them is almost impossible," she says. "It's getting to the stage that I'll have to buy the first thing that fits me, rather than something I like.

"It's all the same stuff that you can get - black skirts with elasticated waists and beaded jackets. It's as though shops think that women over a size 16 only want to wear those clothes. I'm not suggesting I want to wear something that would look good on someone that's a size eight, but there's a balance to be struck and it's not happening right now."

Tricia Chennell, a fashion advisor for John Lewis, agrees. "There definitely isn't the same level of choice in those size ranges," she offers. "It's my job to put together a look that suits each individual woman to hide all those lumps and bumps.

"Sometimes I have to pick and choose from a few brands before I get it right. Up to a size 20 the choice is normally OK, thanks to brands such as Alex and Co and Chesca, but anything above that and the women really do start to struggle with the choices available."

Indeed it seems that for many high street stores, having a good plus-size department is a bit of an after-thought. Even if the size ranges are available, there are often problems with the fit, length and styles of the clothes on offer. While it would be unfair to suggest that this is a disastrous situation for plus-size women, it's certainly far from being perfect.

As Scott points out, "A lot of women who are my size are already going out to the shops with a negative body image in their minds. Not finding any clothes which are stylish and that fit properly only affirms that belief. If someone could get it really right, there would be massive customer demand. As things stand, everyone is missing out. "

Top five tips for shopping success


1. Finding plus-size fashion can be difficult. For trendy clothes, stick to high-street stores such as New Look and Dorothy Perkins.

2. Don't just shop for dark colours - hiding behind dowdy hues will do you no favours. Opt for seasonal colours and mix them with your existing wardrobe.

3. Find a good alteration service that you trust. As many plus-size styles are designed with taller women in mind, you might need to take up trousers and skirts.

4. Be aware of fashion. Don't assume that plus sizes rule out every catwalk trend on the planet. Instead find the looks that work for you each season - and stick to them.

5. Make an impact with shoes and accessories. If all else fails, a jazzy handbag or chic pair of wedges will look good with any kind of outfit. Necklaces, earrings and belts work well, too.