Agriculture is no longer on Britain's agenda. The three main parties barely mention it in their manifestos. All we need is what we've got: the free market and hi-tech. We can buy food from Brazil more cheaply than we can grow it, so we should. The GM companies tell us that they can make new crops to order and have graphs to prove it, and that's science, which cannot be denied. So we should just leave farming to companies such as Tesco, Cargill and Monsanto, just as we have done for the past 40 years. Only the Africans are starving, and that's because they haven't got on the bandwagon yet. This, in a nutshell, is Britain's food and farming strategy.

It is gross: horribly misguided, if not downright dishonest at every level. The simple-minded, neoliberal market never works as promised and, for agriculture in particular, it is a disaster. First, it requires everyone in the world to produce as much as possible - yet this is almost never necessary and, in the long term, is immensely destructive. Second, it demands "value adding", which means feeding grain and soya to cattle and pigs - which is, at best, a horrible waste. Third, farmers are urged to cut costs. So workers are sacked and husbandry is simplified - farming replaced by industrial chemistry. So here is yet more waste, and huge environmental and social damage.

In absolute contrast, farming that could feed people without wrecking the world must conform to the principles of basic biology. It must be maximally polycultural, as nature is - meaning mixed and integrated. It must keep inputs to a minimum - implying quasi-organic. And it must be labour-intensive, because such farming is complex.

The crudity of today's agricultural science and the particular vogue for GM food beggars belief. Under controlled conditions, GM crops may yield more heavily than conventional crops, or prove more pest-resistant - but not always. In real field conditions, over time, they often do less well - due to factors that could not be taken into account in the controlled trials.

There are usually better ways of raising crops, but these alternatives are not explored because the biotech companies are in charge of the research. Thus, in parts of India, traditionally grown cotton has fared better than the expensive GM cotton because the latter could not withstand the drought. For over a decade, mixed, interbred varieties of conventional crops have fared far better than any single crop, GM or otherwise, because they can cope with a greater range of conditions.

More fundamentally, any true biologist knows that the environment, where real farming is practised, is intrinsically unpredictable. It conforms to rules of cause and effect that the physicists call "non-linear". Experiments in the lab and the controlled plot do not replicate the uncontrolled conditions of the wild. Traditional science (including GM science) has serious and obvious limitations.

All this is ignored because there is big money in biotech. The money controls the propaganda so the GM zealots prevail, while the doubters, who include some of the best agricultural thinkers, are ridiculed.

Clearly, the rot goes deep - right through science and economics and with implications for all formal education. But none of the prospective governments seems aware of any of this. As long as they are content to rearrange the deckchairs on the Titanic, I am not sure I see the point of voting for any of them.

Mark Lynas returns in August