That the trend has spread to the realm of interior decor demonstrates the power that TV has over consumers, and, moreover, is another valuable income stream for broadcasters as well as design vendors.

The system works like this: set designers in search of the right scenery for their shows, source from hundreds of furniture and furnishing suppliers. Once a particular item is chosen - be it a couch, an armoire, a particular paint shade - the details are listed on the show's website, with a link that takes users directly to the vendor. Vendors are, for the most part, happy to be associated with a top-rated TV show, while production companies get to use items without having to pay for them, and sometimes even charge the vendor a fee to be part of the set.

For many decor-related companies, the exposure is invaluable. New Jersey-based Benjamin Moore, which makes premium paints, has been chosen by numerous set designers and TV shows for its line of upscale paint colours (with names such as Philipsburg Blue and Provence Creme). The paint used on Desperate Housewives houses, and in Queer Eye for the Straight Guy home makeovers, was also recently seen on an episode of The Sopranos.

'As a brand, we've enjoyed a lot of exposure, mostly unpaid for, through Hollywood and the movies,' says Robyn Spritzer, the brand's senior marketing manager.

The alliance with Desperate Housewives has reaped unexpected benefits: as soon as Benjamin Moore was revealed to be the paint supplier on the housewives' homes, the company was given a two-page spread in People magazine.

'Here are these beautiful homes and colours, with these vivacious women living in them, and it really made a statement for our brand,' says Spritzer.

He concedes that it would be difficult to judge the tangible results of the tie-in with TV shows, but says that the exposure has led 'thousands of people' to click onto the brand's website to look for retail outlets that carry the paint. 'It's going to become more and more important that you're part of the show, not just an adjunct to it,' says Spritzer. 'And we're learning more and more how to get involved with the right programmes.'

Shows with a high visibility in the right demographic are always the most sought-after among design companies. The high-profile suite in Trump Tower in The Apprentice was furnished by the Bombay Company, with tapestries from Corona Decor. The Queer Eye's 'design doctor', Thom Felicia, chooses modern pieces for his remade interiors. These include cantilevered chairs and sleek console tables.

Los Angeles-based lighting designer Cindy Ciskowski has had her custom-made lighting appear on shows such as Sex and the City, The Mind of the Married Man and Queer Eye. But her affiliation with The Apprentice - she worked on the suite a couple of seasons ago - came about as a result of a collaboration she had with KB Homes, a big national housing developer in the US.

The set designer on The Apprentice tracked her down and asked if she'd be interested in lending some of her lamps and other lighting to the show. The producers paid the shipping costs, but didn't have to pay for the equipment itself. And the alliance paid off for Ciskowski.

'It's a growing trend for any retailer to be involved in something like this, and it's a new idea to help get the name out there,' Ciskowski says from Foshan, China, where she has business links. 'It helps to build the whole brand.'

Once her lights, which included table and floor lamps, lampshades, wall sconces and ceiling fixtures, were shown throughout the set of The Apprentice suite, Ciskowski could track the reaction. She was then called by the people behind Martha Stewart's show to design the lighting for that. 'We've definitely had a very positive response,' she says.

Shows benefit in many ways. In The Apprentice, for example, companies that are part of the weekly projects (which in the past have included Burger King) reportedly pay up to US$1 million to be part of the series. And shows such as Queer Eye can charge US$2,000 just to have a designer's name and product listed on the website. After Ciskowski's work was shown on an HGTV series, she received a call from Macy's offering her the opportunity to develop lighting for some of its stores.

'I'd definitely be involved in something like this again because the effects are so positive,' she says.

Like other designers, she says it will become an increasingly natural route to take with the imminent arrival of interactive television. Then viewers will be able, literally, to buy items off the screen.

That said, it's not always effective for every furniture brand. Hiatt, a maker of upholstery furniture based in Los Angeles, has contributed pieces to Extreme Makeover: Home Edition, which also consistently draws high ratings and is a crowd-pleaser because it rebuilds homes for people in special or challenging situations.

'We haven't received a single call, or any new business as a result,' says Tasha Pappas, director of sales. 'But we'll keep doing it as a charity.'