In Harvey Nichols, the chic London department store, the label on a pair of Loomstate jeans reads “100% organic”. When did jeans become an ethical issue? The sales assistant is keen to tell me more.

The cotton, it turns out, is grown by Turkish farmers who don’t use herbicides, pesticides or synthetic fertilisers and so avoid contaminating drinking water or killing local wildlife. Then they are stitched in Tunisia before being shipped to the UK via Ireland.

“It’s important to know that they travel by boat,” says the sales assistant. “Air miles are the devil.”

Two tags dangle from these ethically sound jeans. One reads: “Sustainability is the way forward.” The other is the price: £160. How much, one wonders, did those Turkish farmers get, or the Tunisian seamstresses? So, this is ethical Britain, where our social conscience is colliding with our common sense.

Four weeks ago Sainsbury’s placed the largest ever order for fairtrade cotton (bought from farmers for a “fair”, preset price) while M&S launched fairtrade T-shirts and socks. These cost 15% more than the unfair ones, but are flying off the shelves.

Ethics aren’t confined to our wardrobes: a month ago, two travel bibles, The Rough Guide and Lonely Planet, told readers to cut carbon emissions by limiting long-haul travel.

Bono, the U2 frontman and middle-aged messiah, has launched a socially responsible credit card. And David Cameron, the green-tinged Conservative leader, announced he’s installing a wind turbine on the roof of his Notting Hill home.

Not to be outdone, in the budget Gordon Brown responded to years of green campaigning and whacked a £210 road tax on high-emission, gas-guzzling vehicles.

At the other end of the scale, the unguzzly Toyota Prius, the clever car that generates its own electricity, is selling in its thousands in the UK.

As with the jeans, the price of a clear conscience on the road is high. The Prius costs a hefty £17,795. So no surprise that the Co-operative Bank reports that Britons spent nearly £26 billion on “ethical” goods in 2004, up 15% from 2003.

Of this, sales of fairtrade products — which include coffee, chocolate, fruit and flowers — are up an astonishing 40% to almost £200m a year.

All this makes many people feel good about themselves. But just how ethical are we? How do we know what’s ethical and what isn’t? In a country that worships its shops, is it really possible to be an ethical consumer? And do the ethics of the wallet make a blind bit of difference to anything except supermarket profits? Julian Hunt, editor of The Grocer, is sceptical. “The problem here,” he said, “is that there’s really no such thing as an ethical consumer, because consumers are inherently unethical.

“On the one hand organic is growing, fairtrade is entering the mainstream and shoppers are rediscovering farmers’ markets. On the other hand we’re value shoppers who want the best deal on everything.