Gap? Starbucks? On Portobello Road, darling?

Portobello Road has long been the west London haven for the hip and arty and for the kind of celebrity who prefers to hang out in a slightly more edgy, unpolished kind of space.

Actors Joseph Fiennes and Tom Hollander have praised the cafés and cinemas in the area, while broadcaster Jamie Theakston waxes lyrical about the "energy" of Portobello's famous markets.

Gillian Anderson, star of the X-Files and BBC 1's Bleak House, said it is one of the last remaining "sacred streets" in London.

But now residents and traders claim the unique charms of the area are under threat thanks to block-buying of properties and huge rent hikes that are squeezing out small independent retailers.

Anderson, a local resident, said it would be "a disaster" if stores like Starbucks and Gap were to replace Portobello Road's independent shops.

"It has got a whole atmosphere that is unique and special and timeless. To have a Gap there would be horrendous. I wouldn't go there anymore. It would completely destroy it. It would be horrible."

To prevent Nightmare on Portobello Street a campaign group is lobbying Kensington and Chelsea borough council to turn it into a "business conservation area".

Such conservation status would be a UK first, and establish a precedent for hopeful campaigners struggling to maintain individual high street character against the onslaught of the retail chains.

Tim Burke, of the Friends of the Portobello Road, insists the fledgling campaign could lead to such a breakthrough. "We have a very proud history here of challenging planning laws," he says. "What we have on Portobello Road is a delicate ecosystem where the small traders and the market traders depend on each other. It's creative, entrepreneurial and clever. But big brands are beginning to come in."

At a meeting to discuss the future development of Kensington and Chelsea, the threats to the character of Portobello Road dominated proceedings.

Costas Kleanthous, the chairman of the Portobello Antiques Dealers Association, says: "The planners talk about protection for buildings, but we are talking about something wider. We are talking about character. It's not just a case for this borough but for the nation. Portobello is among the UK's top 10 attractions."

He said anxiety is widespread now that a few companies have bought up large numbers of properties and rent rises of 100 per cent are not unusual. Peter Kalyan of art supply store Lyndons has just moved off the street after trading there for a decade. He says he simply could not meet the rent demanded by Guernsey-based UK Investments.

"They wanted between £40,000 and £45,000," says Mr Kalyan. "That was double what I was paying before. These big boys are buying all the properties and monopolising the rent."

Lindy Wiffen, owner of Ceramica Blue, worries she won't be able to afford a rent rise from her landlord - also UK Investments. "Everyone is concerned that we are going to lose what is special here," she says.

Local resident and singer Jason Donovan adds: "I consider this area my home outside Australia. I love it for what it is. I don't want it to turn into Chelsea."

Jeremy Barnard of JMW Barnard - asset managers for UK Investments - says he can't deny that rents have risen, but insists that big retailers are not lining up.