If we believe our audience is four times greater than has been shown, we want that recognised

Bill Ridley, Talksport

The new system, being tested by Carat Insight, appears to show audiences to speech-based stations - including Talksport, BBC Radio 4 and Radio Five Live - registering significantly higher audiences, with some music stations, such as London outfits Capital FM and Kiss 100, doing worse than previously thought.

But the UK's national ratings body, Rajar, says that the Carat test is too small in scale for such conclusions - and has not taken into account changes in radio listening after 11 September.

Talksport chief executive Kelvin Mackenzie is promoting the new system at a conference called The Future Of Radio.

Former Sun editor Mr Mackenzie, who claims Talksport's audience increased four-fold under the new measurement system, believes advertisers are being misled.

Speech stations appear more popular under the new system

Talksport's research executive Bill Ridley told BBC News Online: "If we believe our audience is four times greater than has been shown, we want that recognised."

Rajar measures radio audiences by giving a national sample of listeners a diary to fill in, recording their radio habits.

Carat Insight's system, tested in Slough, Windsor and Maidenhead, uses a "peoplemeter" built into a wristwatch, which records sounds near the user for 4 seconds in each minute.

The information, processed digitally, is then stored and after a week, when the meter is full, the watch is sent off to an evaluation centre for analysis.

Test findings

The proponents of the new system say it is more accurate - and say that in this year's tests some users were also given diaries, and recorded markedly different listening patterns to those recorded by their own watches.

But a Rajar spokesman told BBC News Online that such test findings had to be treated with great care.

"Radio listening changed dramatically after 11 September and they're comparing post- and pre- September figures.

"We are also acting on behalf of the whole national radio industry, whereas Kelvin Mackenize has been testing in one small part of the country."

But Rajar said it was examining a similar methodology itself.

"We're in a long series of tests as we speak, and this should be complete in about 10 months' time," said the spokesman.