They may not be the best-known names in media land. Even so, they are two of the most influential. Between them, Dave and Sue are transforming BBC Local Radio from a public service into the audio equivalent of a pound shop: a commercial brand that will prove a powerful argument for the abolition of the licence fee. Dave and Sue are both 55. He is a self-employed plumber; she is a school secretary. Both have grown-up children from previous marriages. They shop at Asda, wear fleeces and T-shirts, and their cultural horizon stretches to an Abba tribute show. They are "deeply suspicious" of politicians, think the world is "a dangerous and depressing place", and are consequently always on the lookout for "something that will cheer them up and make them laugh".

They are fictional characters - the centrepiece of what is officially known as Project Bullseye. This requires every BBC Local Radio presenter to "target" Dave and Sue at all times. "To develop great radio programming . . . we need to know where the centre of our audience target is and be able to focus on it in all we do." Forget inspiration and originality. Yet Dave and Sue are horribly convincing. BBC management has even made their photographs available, presumably because it believes its staff can't visualise such listeners. Indeed, the only unconvincing things about Dave and Sue are that a plumber approaching retirement should still have a mortgage and that both of them hate bad grammar, which is somewhat surprising because there is no evidence that either ever reads a book or even a newspaper.

This practice of targeting a profiled listener is lifted directly from commercial radio. In London, LBC reportedly broadcasts exclusively to Amanda, aged 42, a professional woman who takes her child to school on the way to work. Her husband is something in the City and they aspire to three holidays a year but usually manage only one. For a commercial station to which audience figures are everything, precise targeting can make sense even if you then subject Amanda to several hours of sport on a Saturday afternoon. For the BBC to follow suit is proof that its primary aim is success in a commercial market. It was not always so.

The BBC began in the 1920s as a chain of local "wireless stations", with 2LO in London, 6BM in Bournemouth and 5PY in Plymouth. By the end of that decade, a pattern of regional broadcasting had evolved, one that survives in Scotland, Wales and Northern Ireland. But thanks to a ruthless campaign led by Frank Gillard, a former war correspondent and later head of the BBC's west region, local radio returned to England in the 1960s, when the Labour government allowed the BBC to set up a two-year experiment. These new local stations were to be financed in part by local authorities: a community that wanted a station, said the government, should help pay for it. The result was that the first eight stations were in Labour-controlled areas.

Radio Leicester, which opened in November 1967, was quickly followed by stations in Sheffield, Merseyside and Nottingham. The experiment was deemed a success, but future funding was to come entirely from the BBC. A further 12 stations opened in the early 1970s, coinciding with the birth of commercial radio. Many of these early BBC stations later expanded to offer county-wide coverage - Radio Medway, for example, became Radio Kent. A further tranche of stations then went on air, bringing BBC Local Radio to the whole of England.

From the outset, Gillard ensured that "managers would be free to provide the programmes which best met the needs of their communities". Even in 1979, Michael Barton (then controller of BBC Local Radio) was able to write: "Despite my title, it would be alien to the whole concept if I told each station what I thought was good for its audience." Each station had its distinctive style and sound. Barton had been Sheffield's first manager, and his first week's schedule included a studio debate about local government expenditure, an arts magazine and several programmes featuring local choirs. The station's original radiophonic jingle played on (local) cutlery now sounds excruciating.

Over the years, most stations developed distinctive programming, offering airspace to local musicians, writers and even actors. Radio Merseyside produced a highly professional soap, The Merseysiders, as did Radio Stoke with The Colcloughs, both co-funded by regional health authorities. Worthy, yes, but then every station had its own education producer. Some concentrated on community education, with Stoke and Birmingham making significant contributions to local literacy campaigns. Others worked alongside the unions and the Workers' Educational Association to satisfy local needs. Several produced programmes explicitly for schools on local geography and career choices - and gave local teachers the opportunity to develop programme- making skills. It was while thus working during the summer of 1969 at Radio Durham that I was given my first BBC cup of coffee by a programme assistant with a penchant for wearing pelmets rather than skirts. She was called Kate Adie.

The stars of BBC Local Radio are not Desmond Lynam (Brighton) and Jenni Murray (Bristol), who have moved on to become household names. They are the broadcasters who have remained staunchly local - such as Billy Butler on Merseyside, the combative Allan Beswick at GMR (Manchester) and Frank Wappat in the north-east. They are still distinctive characters. Many younger broadcasters could be (and are) interchangeable between stations.

It is not the young ones' fault, nor is it the fault of their station managers (or editors, as they are now known). It is the result of central policy. It began with a centrally approved playlist. Increasingly regarded by the BBC as a unified network, the local stations were then given uniform logos and identical on-air promotion. When Radio 2 began to aim for a younger audience, Local Radio was given the task of reaching less affluent, C2DE pensioners - or, as one editor put it, "poor, sad old gits". Now Operation Bullseye has decided that old people are getting younger, and that they all want the same thing, wherever they live.

Breakfast shows must be all-speech, but "that doesn't mean all news". So Radio Norfolk's once-authoritative breakfast show (formerly required listening for all county and city councillors) is now dominated by fatuous phone-ins. Similarly, a typical half-hour segment of the Peterborough breakfast show from BBC Cambridgeshire includes five minutes of news, three short reports or interviews and 14 minutes of prattle from a presenter and his sidekick, inviting listeners to name a television theme tune and reading out e-mails and text messages.

The BBC's Local Radio directorate may trumpet its audience figures and point out that Operation Bullseye requires stations to provide an "up-to-the-minute news service", "space for local issues to be debated in depth" and "information which helps [listeners] live their life". But the directorate is also demanding the same brand nationwide: output that makes Dave and Sue chuckle. Dave and Sue don't want arts or political coverage, controversy or even reality. In fact, they don't want local public service broadcasting - which is why it is no longer on offer.

David Self was radio correspondent for the Listener