Johann Hari: I like to be informed – but TV's not helping

It's easy to forget as we bullet down the information super-highway, but 67 per cent of British people still get "most" or "all" of their news from the old-fangled flashing box in the corner of the living room. (And kitchen, and bedroom, and kids' bedrooms, and... hey! Put down the remote and listen to me.) But something sad is happening on that box. Politics – the democratic debate that determines our fate – is slowly, steadily disappearing, or being rendered ever-more useless. Where the top-ranking politics shows used to be, there is now a message: We're sorry if your picture has been disrupted. Normal service will not resume, ever.

This weekend, another little light went out. The BBC axed one of its best politics shows: Head 2 Head, a simple – and very cheap – format where two intelligent people argued over the week's news for half an hour. There were no flashy graphics or gimmicks. Polly Toynbee would fight it out with Tory MP Michael Gove, or Bruce Anderson would snarl at Yasmin Alibhai-Brown.

Now it is gone. The BBC tried simultaneously to axe its partner show Dateline London, and only relented when its doughty producer, Nick Guthrie, found a sponsorship deal. ITV has gone even further, cutting away almost all its political coverage outside the nightly news. The Dimbleby show – which pulled in more than a million viewers – was killed by cutting out the studio audience, messing around its time slot, and finally euthanasing it altogether. Its successor, The Politics Show, lasted a few months before also being sent to toast in Politics Hell. It sole political programme now is my colleague Steve Richards's excellent political edition of GMTV – which goes out at 7am on a Sunday.

Jonathan Dimbleby tells me: "What's happening is deplorable. If you use the public airwaves, you have a responsibility to deal with the great public issues of the day, but that is happening less and less." This depresses me, because I was born into a family that didn't know anything about politics. My parents had never voted, feeling it was an alien sphere – so I acquired the taste from stumbling across programmes like Question Time and Brian Walden's interviews.

While there are still oases of serious coverage – Newsnight, Panorama and Channel 4 News can be excellent – much of what remains is being corrupted. The BBC has given almost all its high-profile politics slots to Andrew Neil, whose bias is increasingly outrageous. He persistently quotes quasi-studies by dodgy hard-right US think tanks as "evidence", and when his interviewees cavil, he mocks them – with all the authority of the BBC at his back. For example, when Neil was recently interviewing Sir David King – Britain's former Chief Scientist – he accused him of being part of the global warming "Vatican" that suppresses brave denialist "dissent". He wheeled out every hoary old denialist claim.

Didn't scientists say just as certainly in the 1970s that we would all freeze? (No, one scientist said it, once.) Hmph! Don't the scientists disagree on whether man is causing this warming? (No, within the peer-reviewed literature there is overwhelming consensus.) Neil was exposed by King – he didn't declare it – to be relying on "facts" from the American Enterprise Institute, a Washington think-tank that has taken $1.6m (£800,000) from the denialist oil company Exxon-Mobil.

Similarly, when Neil was interviewing the Labour minister Caroline Flint, he asserted as fact that the near-abolition of welfare in the US (after a two-year lifetime limit) has not increased child poverty. When Flint rightly disagreed, he offered a study by the barking-right Heritage Foundation as "evidence" she was wrong. If a BBC host was this biased to the left, the conservative press would scream for a sacking.

What is the effect on British politics when television coverage – the public's main way of learning about how their country and planet is run – is distorted or disappears? Democracy doesn't work properly. Look at the current London mayoral elections. If you go through the polling issue-by-issue, the London electorate agrees with Ken's policies over Boris's by a very large margin (with the single exception of immigration). They also think Ken is more competent than Boris. Yet it looks likely they will elect Boris next month. Why? Because they don't know the policies. The media has simply failed to tell them: it has offered them a London game-show instead.

Vital issues simply aren't explained to the public – so we cannot vote intelligently. Over the past week, there has been a blazing example of this. Greg Clark, the shadow minister who is considered one of the leading Cam-eroonian thinkers, revealed a major policy change. He described the government's policy of providing tax credits to low-income families as "undesirable", and akin to the subsidies handed out to failing nationalised industries in the 1970s. It is now clear that a Tory government would abolish them, and force the people at the bottom to subsist on whatever the market alone gives them. Meanwhile, Cameron demanded once again that Britain withdraw from the European Social Chapter – which would mean an end to basic rights for part-time workers.

Here are policies that affect tens of millions of people in this country. It is one of the few remaining gaps between the main parties, and it passes the TV producers' tedious test: it affects you, the viewer, directly. There are more than 10 million part-time workers in this country who would suffer, while Labour's tax credits have lifted two million children – including several of my relatives – out of poverty. Thanks to them, there are far fewer children on the sprawling estates here in East London sleeping in kitchens at night, or in damp, asthma-inducing bedrooms. They will soon sag back under Cameron. So where was the coverage? Where was the debate? The television news spent hours raking over the fact that David Cameron rode through a red light on his bike, and Gordon Brown got lost in Windsor Castle for two minutes – but I could find nothing about this. The first the electorate will know is when they lose the money and rights, after obliviously voting for it to happen.

In the midst of all this, the Conservatives have offered a way to make it dramatically worse. They are now committed to ending the requirement for non-BBC broadcast news to be objective and non-partisan. In theory, this would allow a flowering of all sorts of political programming. In practice, TV channels are owned by super-rich Murdochs or Berlusconis who would use "their" channels to push their politics. Our political debate would become even more polluted with invented grievances. The real issues – global warming, say, or the worsening news that in Iraq the Shi'ite is hitting the fan – would be garbled even more than they are now. For Fox sake, this mustn't be allowed to happen.

At its best, TV is a tool of democracy, a way for us all to see our leaders being confronted with the truth. But instead, it largely consists of the airless circulation of ignorance, while the real decisions in the real world are taken somewhere else – beyond the awareness of us, the people.