Twenty years ago organic food accounted for a tiny, tiny niche in the market, with sales of just £5m. Now sales have reached £1.6bn p.a. and strong growth continues. With retailers, farmers, packaged foods suppliers and consumers embracing organic food across all categories, the movement is thriving. Something like 75% of UK households have bought organic foods at least once over the past year - and 40% of these buy organic regularly in their weekly shop.

Few successes, however, are unqualified. Consumers and commentators have posed awkward questions. Although under EU law all food sold as organic must be inspected and certified, with sales having risen at such a fast pace there is emerging concern as to whether standards are being applied consistently and robustly. Put simply: how organic is organic?

Last month, an alleged free-range egg racket was uncovered in the Midlands, where battery eggs were being marked up; an Irish food shop has been found guilty of selling normal broilers as organic chicken; a recent TV documentary found widespread abuse at farmers' markets in the West Country. Suspicious consumers are told to demand to see traders' organic certification.

Burgeoning demand for organic food has also led to supply problems, with insufficient UK availability of some lines leading retailers to import. For the socially responsible consumer, this creates a headache. Organic food should ideally be good for the planet as well as for our bodies but if it has been shipped in from far away it can hardly be said to be environmentally sustainable. Will locally sourced food become more compelling?

The Soil Association, by far the largest and best known of the UK's 10 organic certifiers, has recently come under fire for stretching itself too far, notably by extending certification into fish farming. An Observer Food Monthly article argued "there just isn't enough clear blue water" between conventional salmon farming and organic.

But the Soil Association says its decision to grant aquaculture full organic status in July came only after eight years of deliberation, culminating in a three-year research project that largely answered outstanding issues.

"There has been an inevitable backlash in the media because the organic market has grown so strongly," says a spokesman. "We've taken a bruising in certain areas such as salmon farming, which is controversial because to the purist, migratory fish shouldn't be in a pen. But if we don't get involved, who's going to use leverage on this industry to improve?"

Ideally, says the association, all food would be naturally produced, locally sourced and fully organic. But pragmatism is necessary.

The RSPCA, which owns the Freedom Food standard, is also keen to work with the certifying bodies to clear up other areas of confusion. The RSPCA's John Avizienius says: "Many consumers are confused because they assume organic also implies high animal welfare - but this is not always the case."

Alongside a growing desire for more organic food, people also now want local, says Friends of the Earth senior campaigner Vicki Hird. FoE says it should not have to be a choice between one and the other and is campaigning for policies that favour both organic and local.

Hird would like to see certifiers go further in standards, banning certification of airfreighted produce. On the whole, though, she believes organic standards are rightly respected. "There are flaws, inevitably. Organic needs to be reviewed and improved constantly. But consumers are well aware organic can offer a better option, fresher, free from nasties such as antibiotic and pesticide residues, and using less energy in production."

Leading supermarkets have made strong commitments to organic this year. Sainsbury's became the first supermarket to sign a contract for its British organic beef supply in April 2006, ensuring stability in the marketplace for farmers. If it can be produced here, then it will source 70% of organic food from the UK.

In October, Tesco announced it was to pay the costs of organic inspection and technical support for all existing and new organic dairy farmers for the next three years. It is also working with the Soil Association to improve organic supply overseas. "Our next major initiative is to incorporate our Nature's Choice programme within organics as a requirement to supply Tesco," says Tesco Organic category technical manager Ian Reed. "For many, produce is the entry into organics. It is critical to the success of our overall organic business. It's why we have four technical and commercial people focusing only on organics."

How much organic drives sales is dependent on category. Simply Organic co-founder Belinda Mitchell says it has a huge effect in some categories such as babyfood, and growing impact in many others as consumers come to understand what organic stands for. "Consumers will pay a premium and understand there often needs to be one, but don't want to be ripped off," says Mitchell. "Customers do want genuine products with a genuine heritage and personality. They want to know where they have come from, which is an advantage for organic brands over own label.

"Locally sourced is good for this heritage/provenance reason. Locally sourced and organic is even better! Organic food, though, is as much about individual healthy-eating as it is about environmental issues for most consumers."

Labeling is vital in conveying the organic message. Current EU regulations are designed to ensure consumers are not misled. Labels on foods described as 'organic' must include the certification body.

Nevertheless, food labelled as organic is not necessarily 100% so. There are sensible and practical reasons for food that is not completely organic being labelled as such, but this can cause unease. "EU regulation recognises that it is not yet possible to source all ingredients in organic form," says Rachel's Organic marketing director Steve Clarke. "The manufacturer can use up to 5% of certain authorised non-organic food ingredients and still label the product organic.

"However GM ingredients are never allowed. For foods that contain 70-95% organic ingredients, the word organic is only allowed to appear on the ingredients list and as a description on the front of label to show the percentage of ingredients that are organic. There are not many foods like this available in the UK."

Ensuring standards continue to be tightened and are adhered to rigorously will be vital to sustaining its growth. Organic Monitor director Amarjit Sahota does not expect to see a consumer backlash, but thinks if the number of cases of fraudulent labelling were to rise, this could alienate consumers.

"Demand for organic foods is based on consumer trust they have been produced according to organic methods. If this trust is eroded, then demand would go down. This is why it is very important to ensure the integrity of production methods remains high. It is just as important to ensure the number of fraudulent incidents remains low."

Given the pressure for high standards, and the advance of functionality, fairtrade and locally sourced, the organic sector must be diligent if it is to stay on track.Timeline

1946 The Soil Association inaugural meeting

1960 First organic shop, Wholefood, opens in Baker Street, London

1973 First symbol for 100% organic produce granted to Aspall apple juices

1983 Prince Charles backs organic farming

1985 Safeway pushes organic veg

1986 Turnover of organic produce reaches £5m pa; Sainsbury's tests organic fruit and veg

1990 Sainsbury's launch own label organic milk

1993 EU regulation requires all foods sold as organic in Europe to be certified by law

2001 Soil Association Biodiversity report proves

organic farming delivers more biodiversity. UK sales of organic products reach over £900m, although imports account for 65%.

2004 Sales of organic food pass £1bn

2006 Total organic retail sales in UK hit £1.6bn