By Torin Douglas BBC media correspondent

The BBC has five digital radio stations

The BBC was praised for the quality of its digital radio networks in a government-backed report released on Tuesday.

What a difference a week makes. Last week, the BBC was under fire from an independent government review of its digital TV services.

BBC Three and BBC Four were deemed poor value for money in terms of their record in persuading viewers to switch to digital television.

Now the BBC is being praised for its performance in digital radio which, according to an equivalent report, "has been instrumental in driving digital take-up".

Tim Gardam, the former TV executive who has reviewed the BBC's digital radio services for the government, says one way it has achieved this is through its "unparalleled capacity for cross-promotion of digital radio across all of its media".

BBC DIGITAL RADIO STATIONS Asian Network 1Xtra 6 Music BBC7 Five Live Sports Extra What each station does Report at-a-glance

That cross-promotion does not seem to have had the same effect on BBC Three and BBC Four, which have probably had a similar amount of promotion as the radio stations.

But maybe that is because, in the very crowded television marketplace, they do not have the same "share of voice" as the BBC does in digital radio.

Maybe too, it has more to do with the quality of the BBC's digital radio stations.

Gardam says: "BBC7 has been the most significant BBC service in driving digital switchover.

"It has re-invented children's radio as a multi-media proposition and in repeating much-loved comedy programmes, it offers additional value for money to the licence payer."

Tim Gardam reviewed the BBC's digital radio services

But there is a downside to that success, as he points out. Gardam says BBC7 has "been an important factor in the failure of its commercial counterpart, Oneword, which was a potentially high quality proposition".

Catch 22

This is the Catch 22 in these reviews of the BBC's digital radio and TV services.

On the one hand, the BBC has been asked to help drive digital take-up. But, on the other, its commercial rivals have claimed it provides unfair competition for their own fledgling digital services.

The reviews have been looking at the "market impact" of the BBC services, as well their influence on digital take-up. It is hard to score positively on both counts.

The review of the digital TV services by Professor Patrick Barwise concluded that BBC Three and BBC Four had done no damage to their commercial rivals because their audience was so low.

Even the Artsworld channel - which had complained of the competition from BBC Four - was deemed not have been adversely affected by it.

Gardam says that in radio, similarly, "the BBC Asian Network, 1Xtra, 6 Music and 5 Live Sports Extra do not appear to have had a negative impact on their commercial counterparts so far".

Oneword worry

Though he says they have increased listener choice and competition, they do not seem to have exerted a dominant influence.

But BBC7, he says, does.

"Though Oneword may not have succeeded in any event, the BBC's actions in launching BBC7 point to serious lessons for both the Department for Culture, Media and Sport and the BBC in the corporation's future attitude to its commercial counterparts."

In particular, he thinks the BBC should open up its archives to commercial stations like Oneword: "The BBC should examine how it can enter into joint ventures with the commercial sector when considering future archive-based services".

Crucially, Gardam says the BBC's services must evolve in ways that make them even more distinctive from the commercial competition.

He praises the "commendable co-operation between the BBC and the commercial radio sector" in encouraging the take-up of digital radio.

But in future, he says, the BBC stations must be given much tighter remits if their distinctiveness is to be assured.