Kelvin MacKenzie has been an outspoken critic of Rajar

The Wireless Group, owner of Talksport, sued Rajar over failing to implement an electronic measuring system.

Mr MacKenzie said Rajar's refusal to adopt new technology had cost Talksport �1.5m a month in lost revenue.

Mr Justice Lloyd in London's High Court ordered The Wireless Group to pay costs on both sides, estimated at �700,000.

"Rajar may have won a legal skirmish, but the war goes on until technology-based audience measurement is adopted," said Mr MacKenzie said in a statement.

Rajar said in September it would develop electronic audience monitoring by 2007.

The company tested two electronic methods of recording ratings in 2002 and 2003 but decided against adopting them at that time.

'Fatally flawed'

Their refusal incensed Mr MacKenzie, former editor of The Sun, who launched the legal action in March 2004 claiming Rajar's ratings system was "fatally flawed".

Talksport claimed the system currently employed by Rajar - which depends on listeners filling out a diary - robbed it of 4.7 million listeners each week.

The Wireless Group carried out its own survey of listeners using electronic measuring equipment, which put Talksport's weekly ratings at 6.9 million - against 1.9 million through Rajar's system.

Favourable ratings are vital to commercial radio stations, like Talksport, in attracting advertisers.

Lawyers for The Wireless Group argued in court that the company was entitled to compensation for the loss of an estimated �66m in advertising.

Compensation claim

They claimed Rajar, which represents the BBC and commercial radio, became liable for compensation when it decided against the immediate introduction of audiometers in June 2003.

But on Thursday Mr Justice Lloyd struck out the The Wireless Group's claim, saying it had "no reasonable prospect of success".

Rajar said it had been "vindicated" by the ruling.

"It is good news for the radio industry and Rajar, which has had to endure wholly unwarranted allegations against it over the past few years," said Rajar managing director Sally De La Bedoyere.

Mr MacKenzie vowed to make sure that Rajar stuck to its timetable for introducing electronic meters.