This spring, it's a shopping bag.

But the £5 tote bag, designed by Anya Hindmarch, is not just any old bag.

It may look unexciting to the untrained eye, but this little gem is a limited edition environmentally friendly cotton shopping bag, bearing the logo 'I'm not a plastic bag.'

And it's won an army of celebrity fans, from Keira Knightley to Erin O'Connor.

Introduced as a "cost-effective alternative to a plastic carrier bag" the Anya Hindmarch product sold out yesterday within minutes of going on sale at Sainsbury's stores across Northern Ireland.

Belfast's dedicated followers of fashion queued up outside Forestside to bag a bargain - pardon the pun - while other stores in the province were limited to only 30 of the precious product.

In Coleraine, two women even camped outside the local Sainsbury's store all night.

And it's now changing hands on eBay for up to £200.

So what turns fashion-concious fillies into bag ladies?

Are they all jumping the eco-friendly bandwagon, along with Al Gore, or is the 'I'm not a plastic bag' just another must-have fashion accessory, adorned by the cool crowd.

The bag itself was designed by world-famous fashion accessory queen Anya Hindmarch in collaboration with social change movement We Are What We Do.

The aim of the bag is to encourage shoppers to say no to plastic and opt for environmentally conscious shopping bags instead.

While undoubtedly many consumers support the Go Green campaign, the popularity of the bag is more a matter of fashion.

It's limited-edition - always a big seller - and it's worn by some of the UK's leading style icons.

In fact, anyone who's anyone in fashion circles will already own the bag - Kate Moss, Lily Cole and Twiggy to name but a few.

Local fashionista Katrina Doran, who managed to get her hands on one of the bags, explained the secret of its success.

"I do actually believe in the ethics of We Are What We Do, so I consider myself environmentally friendly," she said.

But she admitted the cool factor played a big part.

"Well, it is the must-have fashion accessory of the season and there's no way I was going to miss out on the chance of owning one."

But is the limited-edition shopping bag here to stay?

For a few months, I would hazard a guess - until Kate Moss is pictured next season wearing long johns and a flat cap.