Chair Man: Ron Arad is the art world's favourite furniture designer, and his original pieces sell for hundreds of thousands. Here, he tells Susie Rushton about his latest creations

I'm not very good at keeping promises to myself," sighs Ron Arad, designer-maker of sculptural furniture. We're sitting in his Chalk Farm studio surrounded by prototype sofas, chairs and tables in his signature curvilinear style and Lego colours. "One promise I made to myself was that I was never going to do a rocking chair again. And another was that we were never going to show at the Milan Furniture Fair again."

Arad broke both promises in spectacular style in April, when he presented a new seven-piece collection called Bodyguards. The very-limited-edition metallic objects included, yes, rocking chairs. Made from aluminium so highly polished that it becomes a mirror, the objects could potentially function as chairs or chaises-longues. Others are unapologetically pure sculptures on which no human posterior could (or would want to) rest.

"I think I have, over my career, increased the population of rocking chairs in the world - not a bad thing, but I did say to myself, no more rocking chairs. Enough. And then, when I sat down to think about new technology I'm using to blow aluminium, I started drawing a rocking chair." That sleek silver chair, a hollow hemisphere of futuristic metal, doesn't just rock back and forth but swivels every which way - a motion that Arad terms "omnidirectional".

The show came after a self-imposed exile from the famed furniture fair. Milan, he thinks, "is for furniture buyers". Although he produces numerous designs in industrial quantities for mega-manufacturers such as Kartell, Vitra and Moroso, these latest "studio pieces" are displayed in a manner closer to artworks in a gallery. In fact, Arad is preparing to show his work in a full-scale retrospective show next year at the Pompidou Centre in Paris.

Despite his resolutions, last year he was "seduced" back to Milan by the offer of a glamorous venue belonging to Dolce & Gabbana, whose fame in fashion just about equals Arad's renown in the world of design. "Well, that shows you what promises mean," he comments dryly. The first D&G-sponsored Ron Arad show, in 2006, called Blo-Glo, was protected by the fashion house's black-clad security guards. His friends mocked him for having so many "bodyguards" protecting his honeycomb chairs - hence the name for this year's offering. "But also, one of the pieces looks very much like a torso. And once something gets a name, the name begins to affect it. And the 'Bodyguards' are huge. They are big. Monsters. But then you cut them and on the inside you reveal another colour inside. They are very labour-intensive."

Arad was born in Tel Aviv, Israel, in 1951. He initially trained to be an architect, moving to London in 1973 to study at the Architectural Association. At his first job in Hampstead, Arad realised he didn't enjoy working for others. One afternoon, instead of going back to the office after lunch, he wandered into a scrap yard, picked out two abandoned car seats, some metal frames and experimented with fitting the parts together to make armchairs. The Rover Chair (1981) would become an icon of the decade. The same year Arad set up his own design studio with Caroline Thorman in Covent Garden, One Off Ltd, developing his aesthetic that combined objets trouves and hi-tech materials.

One of those original Rover Chairs is propped up on bricks in the middle of Arad's studio today. "The British car industry was going down the drain at the time," he recalls, "but this seat was incredibly comfortable. It made sense to do it, and it connected with my interest in ready-made art. Now, some 25 years later, we are redesigning it. It's going to be like the new Mini to the old Mini, the new Beetle to the old Beetle. It's going to be made by Vitra. For the first time I'm designing a retro piece."

Arad has always striven to be contemporary. Other stand-out pieces of his early career were the Transformer (1981), an airtight PVC envelope resembling a shiny duvet which the user can mould to fit their body; the Bookworm shelf (1994), a flexible length of raw steel that can be curled into numerous curvy shapes and mounted on the wall, and which was developed into a bestselling product in semi-translucent plastic by Kartell; the Well-Tempered Chair (1986), a cartoonish armchair cut from tempered steel but oddly comfortable. At that time in London, Arad recalls, there was no furniture-design scene to speak of. "It forced me to invent my profession."

As the big Italian furniture manufacturers began to queue up to produce his surrealist designs in mass quantities, Arad became a household name. For Alessi, he has designed everything from watches to cocktail shakers. In the Nineties he was commissioned for numerous restaurant and retail interiors, most famously the Belgo beer-and-mussels chain; in 2001 it was the technology floor of Selfridges in London and, in 2003, the interior of the Yohji Yamamoto store in Tokyo.

So recognisable is Arad's aesthetic now that he recently found himself the victim of counterfeiting on a vast scale. He's seen Rover Chairs for sale, he says, that are fakes. "When I was in Hong Kong, a contact of mine told me that there are 11 factories doing my 'Vac' chair, and would I like to visit one. So we went out by boat to mainland China. It was very weird. There were Eames chairs and my chairs. I sat down with the guy who ran the factory and told him that I wasn't angry with him, because of course he's creating wealth and employment. But the people in the West who deal with these fakes aren't nice people and why don't we try and get you to do some original designs instead. He said that would be his dream. So that's something I'm working on - me and globalism."

Another issue that troubles Arad is the attempts made by others to try to define his work, often asking of furniture, "Is it art?" According to the art market, it is. Furniture by living designers such as Marc Newson is now fetching sums approaching a million dollars at auction. The price boom is partially driven by American collectors who have covered their walls in art and are now looking for equally exclusive furniture. Spawning fairs, specialist galleries and awards worldwide, "Design Art" is the newly minted term for nominally functional objects that are treated by curators, collectors and press with the same reverence usually reserved for painting and sculpture. "Why do people need to know what it is?" asks Arad, "Why can't people just turn up and say, 'Wow!' We can enjoy it, hate it, love it, be offended by it - but there's no need to categorise it. Putting things into categories doesn't give you freedom as a creator, nor does it let the audience enjoy stimulation. Besides, it's quite pleasurable to look at something and not know what category to put it in. I have no problem designing things to sit on shelves in shops, but we're also very successful with our "studio" pieces that are sold on the art market. I think," he says finally, stretching back on a crazily wave-shaped blue dining-room chair (Plastic Fantastic Elastic, since you ask), "the division is between hideous boring things and exciting things."