Why a 99p dress is bad for fashion

There's been quite a bit of fuss over the past few days over a simple one-piece dress. Made of elastene and viscose, it's a figure-hugging design that comes in a broad set of colours and sizes. Why all the interest?
The designers, OMG Fashion, are selling the dress for less than a quid.
There's already been some kickback as to how a dress that sells that cheaply can possibly be made without resort to sweated labour. OMG, who are based in Manchester, robustly deny any claims that their clothing is being made unethically. They say:

"It's manufactured in Leicester and bound by UK laws. It costs us more than 99p to buy this dress, we are clearly making a loss, it is a PR stunt. The dress is made in the UK."

There are plenty of sweatshops in the UK, but let's take OMG's word that they're doing the right thing. One thing's for sure. As an exercise in PR it's drummed up a lot of attention. Good Morning Britain host Kate Garraway posted a picture of herself in the dress, and it's been all over the press. The quote that made the point for me, though, was one from Kirsty McCrum of the Daily Mirror on the quality of the dress...

Made from 95% viscose and 5% elastane, it's clearly not for girls who enjoy natural fibres close to their skin, but at that price it may persuade buyers for a one-time wear.

And therein lies the problem. The dress is clearly designed to be a disposable item. Let's do the maths. You'd struggle to buy a newspaper, a bar of chocolate or a loo roll for 99p. These are use-and-chuck items. Once again, it shores up the idea of fast fashion as a "wear-it-once-and-bin-it" philosophy.
The last thing we need is more clothing in landfill, when millions of tons of unwanted clothes end up at the tip every year. I have the feeling that, flimsy as OMG's dress is, it's not biodegradable. That would be something worth celebrating. Wear it once and compost it? I'm all over that idea.
There's a market and a need for cheap clothing, but why make it as throwaway as a pair of paper overalls?