'I'm kind of worried about what to get my mum. Her birthday's coming up,' admits Rachel Kesel, a 26-year-old geography student at San Francisco State University. The reason for the anxiety is that she is six months into a one-year pledge not to buy anything new - underwear and a few other essentials aside.

Kesel and 10 of her friends bought no new items in 2006, and many have renewed the 'compact', as their pledge is called, this year. Their abstinence includes not buying presents, which makes birthdays a challenge. In the past, Kesel has given creative non-materialistic gifts or donations to good causes. 'I just don't think my mum gets why I'm doing this,' she says. 'She knows I love her, but she's going to think I'm such an ungrateful brat.'

It might be easy to dismiss the compact as a West Coast fad, but it appears to be on the verge of spawning an international pro-environment, anti-consumerist movement. Some 8,100 people have joined its online group and other 'compacts' have sprung up in places such as Iceland and Hong Kong.

The name comes from earlier pioneering puritans, the Mayflower pilgrims. The 'Mayflower compact' was their civil agreement to abide by laws created after their arrival at Plymouth Rock in 1620. The 21st-century 'compacters' commit to swapping shopping for borrowing, trading or building from scratch in a programme of self-denial. It means they cannot buy anything new for up to 365 days, with a few exceptions for health and hygiene reasons. This is hardcore: they are only allowed to buy new underwear (nothing fancy) and socks.

The original compact members are reluctant ambassadors for the movement. 'It started with four of us over dinner one night and that's how it was meant to be, a challenge among friends,' says John Perry, who works in Silicon Valley. 'We certainly never meant to proselytise, not even to our close friends. The issues for me were always to do with sustainability, the runaway consumer and shopping culture, and how destructive those things can be.'

He has two sons, one of whom, at 15 months old, has 'spent his entire life in secondhand clothes'.

So how difficult was it to stick to the deal? 'The real surprise was how easy it was,' Perry says. 'There was very little by way of temptation and compromise.'

New York journalist Judith Levine, author of Not Buying It, wrote about her experience of giving up shopping for a year: 'I felt disgusted with the way the Bush regime and [then New York mayor Rudy] Giuliani had conflated patriotism with shopping after 9/11.' The day after the terrorist strike, Giuliani exhorted New Yorkers to: 'Show you're not afraid... go shopping.'

She decided to try 'an experiment' not to shop. 'One of the long-term effects was that it showed me that I could happily live on a lot less, and that has made me better able to save and to plan my financial future without thinking "to hell with it, I'll never retire".' She also cleared her $8,000 Visa bill.

Perry believes that by refraining from buying, he saves 'a few hundred dollars a month on unnecessary and impulse purchases' and thousands every year on larger buys like furniture and kitchen appliances: 'The extra money means we now overpay on the mortgage and contribute more to the kids' college funds.'

Of course, many in Britain will find it a bit rich taking lessons on socially aware consumerism from the US. 'I don't think we're as shouty about it as they are in the US,' says Vicky Kingston, of charity the London Community Recycling Network. 'A lot of people do the same thing over here, but just plod along doing it.'

The success of websites such as Freecycle (where you can give away or pick up unwanted stuff, free of charge) or eBay represents a new trend toward recycling as well as a rejection of consumerism. Charity shops are also recording brisk business. Shelter reports 'a steady year-on-year increase' in the number of secondhand items being brought into its shops by the public.

Jenny Greenfield, deputy director of trading at Shelter, believes that the likes of Kate Moss and Chloe Sevigny have made the thrift-shop 'look' hip again. 'More than being just another fashion trend, it also suggests a growing awareness in people's minds about the importance of recycling, reusing and raising money for charity, rather than just throwing unwanted items away,' she says. Oxfam alone says it sells 3 million secondhand items, including 16,000 tonnes of clothing, every month.

How to be a compacter

The aims

· To go beyond recycling in trying to counteract the negative global environmental and socio-economic impacts of consumer culture, to resist global corporatism and to support local businesses, farms, etc.

· To cut clutter and waste in our homes.

· To simplify our lives.

The rule

· Don't buy new products - borrow or buy used. The exceptions are food, drink, medicine (no elective treatments like Viagra or Botox), necessary cleaning products but not equipment (a new Dyson, for example, is not allowed), socks and underwear (utilitarian only) and pyjamas for the children.

To find out more about the compact http://sfcompact.blogspot.com/