Ofcom, the Blair administration's supra-regulator of broadcast media and telecoms, appears to be flexing its muscles in areas outside its direct remit.

The BBC, alone among UK broadcast media, is not answerable to Ofcom but to its own board of governors, a situation that does not best please its commercial rivals - nor, some believe, Ofcom itself.

Nonetheless, this has not prevented the regulator from using public money to commission a study into the BBC's cross promotion of its own radio stations and channels.

The study claims that BBC radio stations enjoy the equivalent of £17 million ($31.42m; €24.27m) annually in BBCTV promotional airtime, more than twice the amount spent on advertising by commercial radio stations.

Says Mark Jankowski of DGA Metric, which conducted the survey on Ofcom's behalf: "The annualised BBC radio promotional spend is the equivalent off over £17m, which would amount to twice that of the entire commercial radio market."

According to the study (conducted between April and July this year), Radio 5 Live - a sports oriented station - was supported by an estimated weekly spend of nearly £180,000. Radio 4 benefited from nearly £24,000 and Radio 1 just over £4,800.

Janowski conceded, however, that the period measured was atypical in that it includes the Wimbledon tennis championships and the Euro 2004 football tournament. Which could well account for the high level short-term 'spend' on Radio 5.

DGA Metric said the figures were even higher if weighted promotions - in which two or more stations may be mentioned or a radio station plugged alongside a TV channel - were taken into account.

The BBC declined to comment on the study, conscious perhaps that there may be an unstated agenda underlying Ofcom's interest.

Data sourced from MediaGuardian.co.uk; additional content by WARC staff