This week, British food makers and retailers will be given guidelines on how to avoid accidentally introducing genetically modified ingredients into products, reports the Financial Times. The industry code of practice will cover everyone in the food chain, including seed suppliers, farmers, commodity brokers and even truck drivers. The objective is to help companies ensure that GM materials constitute no more than 1 per cent of any product. Under the rules of European Commission, any food that exceeds this percentage has to be labelled as containing GM material. The Commission does not, however, specify best practice in meeting the requirement, leaving this to be done by each country. The UK guidelines have been drawn up by the Food and Drink Federation and the British Retail Consortium. They were written in consultation with companies and with the government, and are expected to be announced at the end of the week. The code of practice will cover the cleaning and inspection of equipment such as seed drills, harvesters, silos, shipping containers and factory production lines. The code of practice is expected to include a "know your supplier" component for food companies and retailers. Guidance will be given on how to audit suppliers and ensure that they have trained their staff to recognise the importance of keeping GM components such as grain out of mainstream food. One of the most important themes will be the strict segregation of GM and non-GM commodities on ships and lorries, and in storage. The food industry sees these guidelines as a vital aid to ensuring that companies do not leave themselves open to prosecution by making claims they cannot adequately substantiate. The "1 per cent rule" was introduced last year. The European Commission sought to extend its GM labelling requirements in July, despite opposition from the trade commissioner Pascal Lamy. Europe's strict line on GM food labelling has angered the US, which claims that it discriminates against American products. About 25 per cent of the corn grown in the US this year will be genetically modified.