After the cluster of scandals about fraud and deception on television programmes, Jeremy Paxman used last night’s MacTaggart lecture at the Edinburgh Festival to ask TV bosses to think long and hard about what television is for.

“Television is dumbing down” is one of those treasured national truisms, like the “fact” that exams are much easier these days. People chunter at dinner parties that serious reportage and documentaries have disappeared down the pan along with ground-breaking dramas, classic entertainments and landmark cultural series. I have heard variations of this theme for years, sometimes during interviews with distinguished documentary-makers, such as Sir David Attenborough or Paul Watson. The contents of his lecture suggests that Paxman would happily join the chunterers.

Recent rumours of swingeing cuts to the BBC’s documentary output, especially the excellent Storyville strand, which showcases the best foreign documentaries, do add weight to the complaints. And when John Pilger’s two-hour The War on Democracy delivered one of his ferocious polemical blasts against covert American imperialism on ITV1 last month, it stood out like an angry, throbbing red thumb. Love it or hate it, it was a sharp reminder of the sheer poverty of the channel’s normal documentary output.

Yet for all that, the claim that there are no good documentaries on television isn’t true. The supply may be intermittent, but then it probably always has been. Channel 4’s Dispatches is often excellent. More4 has run brave undercover films about the plight of women in Afghanistan and Iraq. The BBC has broadcast strong analytical series, several by Adam Curtis whose controversial The Power of Nightmares was powerfully balanced by Peter Taylor’s superbly researched series on terrorism in the same year.

Yet the chunterers are right in this sense. Demanding or unsettling documentaries are shunted into late-night graveyard slots or banished to minority channels. And those heavier analyses that do make it into prime time, such as Andrew Marr’s History of Modern Britain, can easily vanish in the multi-channel blizzard. There is so much choice that we blink and miss them. If you surf through the main channels after a hard day’s work, your chances of finding anything that isn’t a property show, reality/celebrity trash or a police series featuring a sexually perverted serial killer are almost nil.

The prevailing wisdom among channel controllers and commissioning editors seems to be that, if you’re going to tackle anything that might cause passing mental discomfort to a Jade Goody in primetime, you’ve got to “sex it up” or at least make it airhead-friendly. It is what a friend of mine once called “the tyranny of the Smartie-crunching masses”.

Some film-makers have perfected this trick brilliantly. You may hate Michael Moore and his methods, but his success in turning the political documentary into a popular art form is undeniable. Following his example, Morgan Spurlock has been happily making exposés of the evils of consumerism into fun for all the family.

BBC One’s effort to sensationalise Panorama is a case in point, leading to that absurd shouting match between John Sweeney and the hectoring Scientologist. And why didn’t Channel 4 let Richard Dawkins make a deeper exploration of paranormal practitioners in The Enemies of Reason rather than confining him to a series of short superficial encounters?

Little wonder so many programme-makers who want to tackle “difficult” issues, have turned to dramatisations. Nick Broomfield has recently joined their ranks, but film-makers like Peter Kosminsky (The Government Inspector, on the David Kelly suicide) have been doing it for years, often to powerful effect.

Ken Loach hasn’t stopped since Cathy Come Home. The problem for viewers is never quite knowing where fact ends and fiction starts, and therefore how much weight to attach to our powerful emotional reactions.

The question remains as to whether we still want our free-to-air channels, with a public service remit, to offer us a balanced diet during primetime — a diet that includes a bit of roughage in the form of serious documentaries. Dyed-in-the-wool populists like Peter Bazalgette like to dismiss their critics as “patronising elitists”, arguing that Big Brother is truly democratic because it gives a voice to the likes of Jade Goody.

Reality television can be hugely entertaining and occasionally revealing, but this argument is the purest humbug. What is truly, madly, deeply patronising — and complacently elitist for that matter — is underestimating the viewers’ capacity to understand and enjoy programmes that shake up their preconceptions and broaden their understanding of the big wide world.

There is a hunger for information, insights and intelligent debate out there. As the controllers and commissioners mix their schedules, they should set aside their terror of low ratings and have a bit more faith in the curiosity of their viewers.

Paxman ended his lecture rightly bemoaning executives’ obsession with attracting the young. Sometimes those executives forget that many young viewers mature and become more intellectually hungry — hungry for material that explains their world. If television forgets how to sate this hunger, the public will desert and find it elsewhere.

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