Radio 4's little sister could soon become the star of the show

2005: Radio 5 Live - The Today programme was once an essential part of breakfast for the chattering

Listen carefully when you switch on, and you might just hear the plates moving beneath the BBC's talk-radio networks. By the end of 2005, Radio 4 will still boast more listeners than its sprightly little sister, Radio 5 Live, but the gap will continue to narrow, probably at a faster rate. A curiously conceived hybrid of 70 per cent news and 30 per cent sport, Radio 5 Live is no longer serving only blokes and ladettes. It is slowly replacing Radio 4 as the listening of choice for those who want to stay abreast of topics that matter to them in 21st-century Britain - the people we used to call the chattering classes.

The figures reveal a distinct trend. Since 2000, listening on Radio 5 Live has been on a fairly constant upward curve that is growing steeper. Taking July to September as the annual benchmark (because that quarter is the most recent available for 2004), 5 Live's weekly reach has grown over four years from 5.4 million to 6.4 million. The most dramatic rise has been in the past year, with an increase of 682,000 - nearly 12 per cent - over the September 2003 figure. Although part of that can be ascribed to the Olympic Games, the general well-being and prestige of the station was confirmed earlier in the summer when it struck gold seven times in the Sony Radio Awards.

Radio 5 Live has always suffered from being available only on two medium wavelengths, both of which give dodgy reception in some areas. Radio 4, on the other hand, can be heard both on FM and long wave, as well as medium wave in the London area. Despite this distinct advantage, the figures suggest that the station of Today faces an uncertain tomorrow.

In 2002, Radio 4 reached a high of 9.7 million listeners a week, fuelled in part by an ear-popping storyline in The Archers steeped in steamy adultery. Last September, it was down to 9.4 million. For sure, this is a very gradual decline, but still it looks increasingly like the early symptoms of Telegraph syndrome: older listeners die off and are not replaced by younger ones, who prefer the pace and immediacy of Radio 5 Live. If alarm bells are not ringing for Mark Damazer, the station's new controller, they ought to be; for, as the Telegraph has discovered, the syndrome can prove irreversible unless treated early.

The average age of Radio 4's audience has crept up over the years, and now stands at 54. Although Radio 5 Live targets listeners between ages 25 and 44, more than half of them are in fact older than that, and the average is 47. That figure, too, is increasing - which suggests that people are not switching their allegiance to Radio 4 as they grow older, as they would be expected to do in a marketing director's ideal world.

The Today programme has long been Radio 4's pride and joy and its strongest ratings performer. It is also the spot that most dramatically highlights the network's deterioration. From a peak of 6.6 million listeners 18 months ago, the programme was down to 6.01 million by September, having shed 150,000 since June. By now, it is probably below the magic six million. In that same quarter, Radio 5 Live's Breakfast programme, presented by Nicky Campbell and Shelagh Fogarty, added 243,000 listeners, taking it to 2.61 million.

It is no surprise that Today is shedding its audience. The programme has become predictable, formulaic, self-important and smug. The familiar mantra that it sets the day's political agenda is the opposite of the truth. More often than not, it follows the agenda set by the morning papers, and since the Andrew Gilligan debacle it has been even less inclined to venture into uncharted waters. The overlong interviews with politicians that follow the 8am news bulletin are seldom revealing. Most of each interview is taken up with the ritual gladiatorial contest in which John Humphrys and James Naughtie make ever longer interventions, spluttering shrilly and turning audibly red-faced as they fail to persuade politicians to confess and repent. Nor has Today succeeded in finding a female presenter with the grip and impact to match, say, the Newsnight trio of Kirsty Wark, Martha Kearney and Stephanie Flanders.

The programme is also surprisingly unprofessional technically. Those of us who listen on long wave are by now accustomed to the risibly clumsy switch to Yesterday in Parliament at 8.30am, while Today continues on FM. Items are curtailed sharply and without warning, while in full flow, and sometimes there is a long silence before YiP gets under way. The Today people, clearly resenting the intrusion into their programme, make no effort to ensure that the switch coincides with the end of an item.

Like the supporters of fox-hunting, Radio 4's hard-core listeners are a tight-knit group, stubbornly determined to resist any change to their age-old customs. The last time I broached this topic in the New Statesman was in 1997 (thank you for waiting), in the wake of a cataclysmic row when James Boyle, the then controller of Radio 4, had the audacity to move the repeat of The Archers from 1.45pm to 2pm, forcing a drastic change to the lunchtime habits of millions.

On the plus side, it was Boyle who gave us John Peel's Home Truths, decried at the time as a symptom of dumbing down. After all, asked the critics, who wants to listen to people chuntering on about domestic trivia when we could be hearing a profound analysis of student unrest in Tbilisi? And wasn't Peel in essence a Radio 1 person anyway? Only as it grew on us did we recognise that the programme was a jewel in Radio 4's crown and its late, lamented presenter a national treasure.

Which brings me back to Radio 5 Live. The success of Home Truths should have alerted Boyle's successors to the way a modern broadcasting station has to develop. Touchy-feeliness, the quality pioneered by 5 Live, is one that, however much we of the stiff-upper-lip old school might deplore it, is in tune with the spirit of the age. Radio in the 21st century has to be interactive, involving people and giving them a chance to respond.

Nearly every strand on Radio 5 Live has its phone-ins, no longer dominated, as they were at the beginning, by adenoidally challenged obsessives, the radio equivalent of readers who write to newspapers in green ink. Victoria Derbyshire's phone-in programme, for instance, which regularly draws an audience of 2.13 million, boasts a range of subjects (private v public morality) and guests (Matthew Parris, Susie Orbach) that could easily attract disaffected Radio 4 listeners.

This is not to say that every hour spent tuned to Radio 5 Live yields complete satisfaction. Sometimes, the topics are less than gripping - the other night, the pundits on Matthew Bannister's show were solemnly debating the nibbling merits of sugar-glazed mini-sausages as against flavoured crisps - but it is seldom long before the conversation reverts to something meaningful, and often the people who call in have relevant points to make.

Radio 5 Live does not have programmes as such, which is why its daily listings take up only half a column in the Radio Times, as against two columns for the highly structured Radio 4. Few of us nowadays settle down in our favourite chairs and listen to the wireless on a pre-planned schedule, as our grandparents did. We are always doing something else, often driving to our next high-powered appointment, and here again listener participation comes into its own. No matter how fascinated I may be by Melvyn Bragg's learned discussion of Etruscan philosophy on In Our Time, I need to know how long I am going to be stuck in the traffic jam on the M4, so that I can call ahead on my mobile. And selfless motorists take the trouble to pull in and phone Radio 5 Live to give a real-time update on conditions.

Such "news you can use" is routinely sneered at by the BBC News establishment - of which, worryingly, Damazer is a graduate. I interviewed Rod Liddle when he was in charge of Today about three years ago and, to my question about introducing an element of consumer journalism into his programme, he responded: "The only possible answer is 'fuck off'." He did just that not long afterwards, but his attitude still survives on Radio 4, where programmes such as Money Box and You and Yours are put into self-contained boxes where they cannot contaminate the news output.

Radio 5 Live, by contrast, is like a Christmas pudding - the ingredients are all thrown into the same bowl and mixed energetically until they blend. In 2004, it celebrated its tenth birthday; by the time it reaches 20 it could be the country's most popular talk-radio station. If Radio 4's decline is to be arrested, Damazer needs to grit his teeth against howls of pain from the glad-to-be-grey lobby and give his network another good Boyleing.