'We don't want parents having to cover their children's ears in the cereal aisle'

Steve, one of four presenters on Asda FM, takes charge of a mid-morning show, and he's unashamedly on message when it comes to the importance of the company and the station.

"Of course I shop at Asda, it would be crazy not to," he says, deleting an Avril Lavigne track and replacing it with a request for Bon Jovi.

"The supermarket has worked hard on its reputation for being family focused, and Asda FM is an extension of that. We're here to reinforce the brand, but we're also here to entertain customers, to make the shopping experience that little bit more pleasurable."

At Asda FM, everything is fun with a capital F. The DJs happily segue from a two-for-one offer on washing powder to an individual store's charity baked-bean bath fund-raiser, and everything is done with a special kind of chirpiness.

Commercial radio may have earned a reputation for Smashie and Nicey broadcasting, and some regard superstore DJs as occupying an even lower rung of the ladder. But the statistics for Asda FM are not to be sniffed at.

Steve's potential audience is not only huge but, crucially, it's also captive. Each week, the station broadcasts to 18 million shoppers and 167,500 staff. Add in the 1,000 or so listeners who tune in via the internet, and Asda FM is a vital and lucrative part of the retailer's overall advertising drive.

In between the likes of Katherine Jenkins and Coldplay, key messages are broadcast twice every hour and in the run-up to important dates in the calendar, special features are spliced between the music.

Earlier in the week, Steve was busy plugging pancake recipes.

"I feel completely connected to the audience," he says. "The great thing is that when you talk about pancakes, you know that customers can immediately go off to aisle six and pick up the ingredients they need. There's a direct link between what you are saying and what they are doing.

"My job is to be one of them. If there's a particularly good offer on, I might introduce it by saying, 'This is so good, as soon as I leave here, I'm going to rush to a store and treat myself'."

Steve says that, occasionally, his mother-in-law will ring to say she heard him while doing the weekly shop, and while he may not have a huge postbag, the station does have a loyal listenership.

Asda FM is broadcast from the offices of Headland Media in the centre of Leeds; the studio is just about big enough to squeeze in a mixing desk and a couple of chairs.

However, behind the scenes, the operation is a carefully orchestrated well-oiled machine and Asda FM is run much like any other commercial outfit.

There's a head of music who chairs a weekly playlist meeting – purveyors of piped music need not apply. Newly-chosen tracks join a catalogue of 10,000 or so old favourites, and with the producers keeping a close eye on shopping demographics, there is nothing random about the order of each day's songs.

After 3pm, when parents are likely to be dragging children round the aisles, Asda stores tend to be ringing with hits from Glee.

On Friday and Saturday nights, they turn the station over to dance and urban music, and on Sunday, the playlist is deliberately gentle to help to soothe hangovers.

Some songs, which don't live up to Asda's wholesome image, fail to make the cut – Eminem is not a supermarket favourite and anything too shouty is given a wide berth.

"Obviously, we don't broadcast anything with sexually explicit lyrics," says Jenni Crowther, a senior account manager at Headland Media and effective station manager for Asda FM.

"We don't want parents to have to cover their children's ears in the cereal aisle.

"We're not here to be edgy, but we do reflect the charts and have been known to be ahead of the game.

"A couple of years ago, Gnarls Barkley's Crazy was everywhere, but the single was, in fact, played first on Asda FM. We all just loved it and it fitted with our criteria. A few weeks later, it was on Radio 1 and from there it shot up the charts.

"Most commercial radio stations have a very fixed listener base, who tend to fall into quite a narrow age bracket. That's not the same with Asda, we have every possible age range and the whole spectrum of backgrounds, so it would be silly not to try to reflect their tastes when we can.

"Record companies treat us just like any other commercial station and one of the great things is that we can react incredibly quickly.

"When I go shopping at Asda, I like to people watch. When you hear people leaving the store humming whatever's been playing on the radio, it's kind of confirmation that we are doing a good job."

With an emphasis on the wholesome and the feelgood, the news headlines inevitably need censoring.

As Steve flicks on to the latest stories running on Sky, it quickly becomes evident this is not a good news day. The international row over the assassination of a senior Hamas military commander in Dubai is top of the bulletin, followed by the inquest into the death of fashion designer Alexander McQueen. Both are rejected for being too hard-hitting.

Another story is shelved because it mentions Asda rival Amazon, and even a seemingly upbeat story about unemployment figures is rejected because the last line contains a less positive forecast.

Instead, the news tends to be a mix of showbiz and upbeat consumer stories – at Asda FM there's no room for doom-mongers.

The supermarket isn't the only firm keen to capitalise on retail radio. From the Leeds studios they also broadcast in-house programmes for Topps Tiles, Costcutter and Carpetright.

Elsewhere in the country there are dedicated stations for Debenhams, Ikea and Morrisons, and one of the main champions is Bruno Brookes. He may still be best known for presenting the Radio 1 charts in the 1980s, but he now runs his own retail radio company.

"More and more firms are realising the benefits of having their own station," says Jenni. "Asda FM actually started 20 years ago, but it was only in 2005 that we brought in live programmes. In the past, we have run interviews with Cliff Richard, the 2007 X Factor winner, Leon Jackson, came into perform live and we are always looking for ways to take the programmes forward."

Just like any radio station, some listeners to Asda FM are more devoted than others. Steve has a few regulars who text in requests during their weekly shop, and one man was so taken with the store that he decided to propose to his girlfriend over the airwaves.

"Mark, from Cardiff, is a regular," says Steve. "He works for Asda, but listens on his days off and always texts in to say hello to his colleagues.

"There's also Joe, from Texas. He got made redundant and somehow he came across Asda FM. He liked it so much he's taken to blogging about the station. In fact, when I get a minute I must remember to see how he's getting along."

Until then, there's Abba to be played and the store's in-house bakery to promote.