Britain's agricultural industry was split last night over claims there is no conclusive evidence that organic food is healthier than products grown by conventional methods.

The row was triggered by comments made by David Miliband, the Secretary of State for Environment, Food and Rural Affairs, who described organic produce as "a lifestyle choice" and insisted that food grown with the use of pesticides and other chemicals should not be regarded as second-best.

His comments came as a blow to the organic food industry, which is keen to obtain official recognition of the nutritional and environmental benefits which it ascribes to chemical-free farming.

Asked about the benefits claimed for organic food in an newspaper interview, Mr Miliband said: "It's a lifestyle choice that people can make. There isn't any conclusive evidence either way."

He went on to say: "It's only 4 per cent of total farm produce, not 40 per cent, and I would not want to say that 96 per cent of our farm produce is inferior because it's not organic." The minister described the rise of organics as "exciting" but he insisted that shoppers should not regard non-organic food as "second-best".

According to the Soil Association, sales of organic food increased by 30 per cent to ยฃ1.6 billion in the UK last year. The association's website states that organic food does not contain many of the additives that are allowed in non-organic food and has shown to have higher levels of vitamins and minerals, as well as being better for wildlife, causing lower pollution from sprays and producing less carbon dioxide and less dangerous waste. About 350 pesticides are allowed in farming, and an estimated 4.5 billion litres of chemicals are used each year.

Organic farmers and associations hit back at Mr Miliband's comments. Pete Glanville, the secretary of the Shetland Organic Producers Group, which farms vegetables and sheep, said: "Our producers are dedicated to producing foodstuff which is free of chemicals . You only have to look at the list of things that goes into creating lots of things to realise just how much we are not putting into our bodies by eating organic."

Mr Glanville added: "We are not saying the other 96 per cent which is farmed conventionally is rubbish, or second-grade. We are making a choice about what goes into our bodies."

However, Peter Kendall, the president of the National Farmers' Union, said he had seen "no evidence" to prove organic food is healthier. He said: "If there's a small but growing percentage of consumers who want a different product, then that's a great opportunity for members. But I have a real problem with conventional methods being demeaned at every opportunity."

Here, two experts make their case for and against going organic.

Hugh Raven

IF THE Environment Secretary, David Miliband, has been accurately reported, his comments are disappointing - but not entirely surprising. It's disappointing to hear he thinks organic food is a lifestyle choice. That doesn't seem to be the view of his department. For more than a decade, the agriculture ministry has being paying farmers to convert to organic production in recognition of the good things it brings.

The wildlife benefits are now very well-established: organic farms typically have more wildlife, a wider variety of species, and more especially of those species that have declined most in the last 40 years. There are other green advantages too. By avoiding artificial fertilisers altogether, and pesticides except under very specific circumstances, organic farming is good for water quality. And perhaps most crucially, by eschewing energy-intensive synthetic inputs and locking up carbon in organic matter in soils, organic farming is far more climate-friendly than its conventional equivalent.

Some people buy organic products for animal welfare reasons. They're right to do so: the main farm animal welfare charities back organic farmers because they respect the needs of the animals and give them a more natural life.

If support for these advantages is a "lifestyle choice", it's one the government makes year after year - through aiding organic conversion to get more of these goods. I think Mr Miliband knows this fine well: he seemed well-disposed and supportive when we discussed it with him recently.

On food and health, Mr Miliband is right that there's "no conclusive evidence either way". This is not really surprising - as it would be highly problematic, and ethically very dubious, to conduct on people long-run experiments able to prove the point. But we do know that a largely organic diet reduces intake of toxic chemicals, increases beneficial vitamins, minerals, essential fatty acids and antioxidants, reduces consumption of food additives and colourings, and totally avoids GMOs. The composition of organic milk has been shown to differ in ways likely to be beneficial to health. The Food Standards Agency has advised that "organic food contains fewer residues of pesticides", so buying organic reduces the chances of eating them.

Many people think it's fair to conclude from this evidence that organic food is better for you. Certainly some sensitive and important groups think so - cancer patients choosing an organic diet, for example, and parents of young children whose buying decisions mean organic baby food now accounts for more than half of the prepared baby food sold.

Organic food is now flying off the shelves. Market growth in 2005 (the latest figures available) was 30 per cent. Political support will inevitably follow.

Hugh Pennington

SALES of organic food in Britain have never been higher.

There can be little doubt that the people buying it believe it is healthier for them than other products, and that this faith is responsible for its popularity. So it is not surprising that David Miliband's comments as a government minister that organic food is a "lifestyle choice" have been top of the news.

His comment that there is no conclusive evidence either way concerning the health effects of pesticides will surprise many. But he is right. Dispassionate analysis of the many studies done over the years searching for the health benefits of eating organic food has found none.

Admittedly, such studies are difficult to do. Two sizeable groups of individuals identical in all respects other than in the way their otherwise identical diets have been grown would have to be compared from birth to death to make the results of such a study scientifically compelling. Such research has never been done. So we have to rely on much less satisfactory evidence.

But no organic advantages have emerged. Neither has any evidence that food grown conventionally using synthesised fertilisers and pesticides is harmful because of their use.

Of course, there is plenty of evidence that food-associated health problems occur. But excessive consumption is the big villain of the piece. It could be said that the popularity of organic food might help here because it is significantly more expensive.

However, this is not true for another very common group of diseases - food poisoning by microbes. Organic food is just as likely to be contaminated microbiologically as intensively farmed meat or vegetables, and for some products more so, as shown by recent research on Campylobacter in chickens.

The lack of any detectable health-giving property of organic food is mirrored by the absence of any laboratory tests that can distinguish it from food grown differently. And those organisations that regulate it, like the Soil Association, define it not in terms of properties as a product, but by the way it is produced.

In my view, this is where the demonstrable effects of organic systems are to be found, like more birds and insects in organic fields. The minimisation of antibiotic use is another good thing - but microbiologists were calling for this long before organic farming became popular.

I have nothing against organic food as a component of the basket of foods available to us in the UK today. I have nothing but admiration for the success of those responsible for marketing it and their ability to overcome the propensity of the public to choose food primarily on price (as shown by survey after survey). As niche products, organic food is here to stay. But from the health point of view, at the end of the day, it is nothing but a brand.

Advertising and lobby groups are very successful in determining our eating preferences and the way we grow our food (organic farming is not unsubsidised). They are parts of a free society. But challenges to their influence should be made from time to time. So I welcome David Miliband's comments. It is also worth noting that the environmental effects of organic systems are not all beneficial. Much organic food sold in the UK is imported. It generates food miles by the million. And a big by-product of animal manure production for organic fertiliser is methane, 20 times more potent as a greenhouse gas than carbon dioxide. Most important, to put organic farming in a global context, it is an undisputed fact that two-fifths of the world's population lives on food whose production is dependent on artificial fertiliser. Organic food will never feed us all.