Beef contaminated with horse meat may have been sold in Britain for 'years' The Food Standards Agency said it was considering taking legal action, which could be against supermarkets or suppliers. Sainsbury's, Asda and the Co-op cleared their shelves of beefburgers bought from the suppliers at the centre of the scandal. Irish scientists said they had discovered that the meat was contaminated two months ago. However, they did not act because they wanted to conduct further tests. Suppliers in Holland and Spain are being investigated for supplying the contaminated meat. The Food Standards Agency said it had not conducted checks in the past because horse meat did not pose a threat to health. However, Tim Lang, a professor of food policy at City University, London, said: "It could have been going on for years but we wouldn't know about it because we have never conducted tests. For too long we have had light touch regulation. The Food Standards Agency has to be institutionalised into taking a more critical approach. They have to work on the assumption that things could go wrong. The scale of horse meat contamination emerged on Tuesday, when the Food Safety Authority of Ireland said it had tested 27 beefburger products. More than a third had tested positive for horse DNA, including one Tesco Value beefburger in which 29 per cent of the "beef" content was in fact horse meat. Tesco blamed suppliers, saying there had either been "gross negligence" or "illegality." As the full extent of the scandal emerged, £300 million was wiped off the company's stock market value. Aldi, Lidl and Iceland also withdrew frozen beefburgers from their shelves after they were found to be contaminated with horse meat. They were joined by Sainsbury's, Asda and the Co-op. While they were not found to be selling contaminated food they said they were withdrawing the frozen products from sale as a "precautionary measure." The supermarkets were supplied by three meat processing companies, two of which were owned by the ABP Food Group, based in Ireland. ABP said it was investigating two of its suppliers, believed to be based in the Netherlands and Spain, for selling it contaminated "beef filler." The company has withdrawn 10 million frozen beefburgers from the market, and said it had been "shocked" by the discovery of horse meat in its products. The Food Safety Authority of Ireland said it first identified the contaminated beef in November, but held back from publishing information until it had held further tests. On Dec 21, it alerted officials at the agriculture ministry in Ireland, and sent the samples off for a final round of tests in Germany. The tests were completed last week and the Food Standards Agency in Britain was told on Monday. Patrick Wall, the former head of the Food Safety Authority of Ireland, said "greed" might have led to horse meat being passed off as beef. Consumers have a right to know exactly what is in their food, even though in this case there's nothing more dangerous than horse meat. Mr Cameron told MPs: "Ultimately retailers have to be responsible for what they sell and where it has come from." However, MPs were highly critical of the Food Standards Agency. Anne McIntosh, Conservative MP for Thirsk and Malton, said: "In North Yorkshire we are the home of the horse and hound. We don't expect to get horse on our plates. The surprising thing is how come our own Food Standards Agency did not pick this up? Why was it left to the Irish? Liffey Meats, in Cavan, the third company named for supplying contaminated meat, apologised to customers. Silvercrest, a subsidiary of ABP Foods, said it was withdrawing products from sale and replacing them with new lines. A spokesman said it suspected European suppliers of being the source of the horse meat. "Following tests carried out by the Food Safety Authority of Ireland, we have been alerted to frozen beefburgers which contain porcine and equine DNA," said a spokesman. Although the products pose no risk to public health, Silvercrest has taken immediate action to isolate, withdraw and replace all the suspect product. Silvercrest has never purchased or traded in equine product and has launched a full-scale investigation into two continental European third-party suppliers who are the suspected source of the product in question.