The Digital Radio Development Bureau - a trade group funded by broadcasters claims that the number of UK consumers listening to DAB digital radio - especially in their cars - will continue "to rise dramatically" as more discover the benefits of increased station choice, digital quality sound, and interference free listening.

The DRDB said the biggest growth in volume is expected to come in the in-car sector and domestic receivers.

"One of the biggest stories to emerge over the next few years will be an increase in the number of people listening to DAB digital radio in their cars," the DRDB said in a statement.

"This, it is expected, will result largely from an increase in dealer fit and factory line-fit by major car manufacturers which will grow from 15,000 units in 2005 to 702,000 units in 2009."

DRDB chairman Ralph Bernard said: "The latest figures… show that DAB Digital Radio continues its healthy climb to mass market penetration in the UK. It is encouraging news that consumers are continuing to buy new receivers to enjoy the new digital stations on offer."

A DRDB forecast predicts that by the end of 2009 there will be around 20 million DAB digital radios in UK homes, up from 1.2 million at the end of 2004, and a 15-fold increase, equivalent to a household penetration of 40% by the end of 2009.

The annual retail market value in 2009 is expected to be £456 million across all product segments compared with £87 million in 2004.

Innovations such as electronic programme guides and the addition of multimedia and interactive services are also expected to boost DAB's growing popularity.

The DRDB noted that there is a potentially substantial market for DAB in mobile phones, portable media players and PC-DAB products, but because it is too early to predict consumer demand for these products with confidence, they have been intentionally excluded from its forecast. Developments in these sectors could lead to a significant increase in overall DAB take-up and it is anticipated they will be included in forecasts.