Radio 1's Mary Whitehouse Experience was recently re-aired on BBC7

The study shows 175,000 radios are now in UK homes and that figure could reach 500,000 by the end of the year.

BBC7 broadcasts archive comedy and drama, as well as daily afternoon programmes for children.

It launched last year as part of a package of five digital-only stations from the BBC.

BBC DIGITAL STATIONS Five Live Sports Extra 6 Music BBC7 1Xtra Asian Network Plus Radios 1-4, Five Live, the World Service, and some local BBC stations

Digital radio - also known as digital audio broadcasting (DAB) - uses different frequencies to traditional analogue services, and listeners benefit from a wider range of stations as well as clearer reception.

The research was carried out by the Digital Radio Development Bureau (DRDB), an industry body backed by the BBC and commercial broadcasters.

Other stations which were persuading people to buy digital sets were Radio Five Live and Talksport, Jazz FM, BBC World Service - all of which are only usually available either on medium wave or in restricted parts of the country.

Digital-only station Planet Rock was also a major attraction, as was the ability to hear Classic FM without interference.

High street sales

The figures showed one in five purchasers were women, while one in four of all buyers had obtained their radios from one high street chain, Argos.

OTHER NATIONAL STATIONS Oneword Planet Rock Core Life Primetime Plus Talksport, Classic FM and Virgin Radio, and other stations which vary by area

DRDB chief executive Ian Dickens said: "Radio broadcasters have been committed to DAB digital radio for some years now, although at times it was a lonely place to be.

"This market data provides credible proof that consumers are buying into DAB."

The BBC's director of radio and music, Jenny Abramsky, said: "This research shows digital radio is on its way to becoming a mass market proposition, rather than the preserve of enthusiasts."

The corporation is now beginning work to upgrade more of its transmitters for digital stations - at present, 65% of the UK can receive them, but this should increase to 85% next year.