Just 24 hours later, however, the Prime Minister's spokesman said: "There is no evidence of health risks...the Chief Medical Officer has underlined that point." The Prime Minister believes that Mr Paterson is "doing the right thing" and that he was yesterday "underlining that it is important to have a testing regime," the spokesman said. Burgers and ready meals have already been withdrawn by Tesco, Findus and Aldi. Professor Dame Sally Davies, the Chief Medical Officer, said there is currently "no indication" that "bute" is present in any of the products that have so far been found to contain traces of horse meat. There is nothing to suggest a safety risk to consumers who may have eaten the products. All of the retailers involved so far have removed potentially affected products from their shelves. Phenylbutazone is used in some people who suffer from ankylosing spondylitis, a type of arthritis. However, there are international checks to prevent phenylbutazone from entering the food chain because there is a low risk of serious effects - such as aplastic anaemia - in some people. As such, it presents a limited public health risk and CMO supports the FSA advice that it should be excluded from the food chain. There is currently no indication that phenylbutazone - bute - is present in any of the products that have been identified in this country, but the FSA has ordered further tests to confirm this. It's understandable that people will be concerned, but it is important to emphasise that, even if bute is found to be present at low levels, there is a very low risk indeed that it would cause any harm to health. It comes as Lord Haskins, a farmer and the former chairman of Northern Foods, said there is "endemic fraud" in the food industry which has led to the horse meat scandal. Mr Paterson has warned the British public that the horse meat scandal is likely to get worse. He has promised that if any health risks are discovered in contaminated meat then he would "take the necessary action," suggesting that some meat imports could be banned. Ministers have warned that tests being carried out by the Food Standards Agency, the results of which are due on Friday, could reveal that more processed beef products could be found to contain horse meat. "We have to be prepared for more unwelcome news," Mr Paterson said. That is why I've ordered this very rigorous testing regime to go ahead as rapidly as possible because it is down to the retailers - they are the ones who are responsible for the quality and safety of what they sell.