The supermarket chains Tesco, Sainsbury and Asda withdrew more than 20 products from their shelves - including Belgian pate, mayon- naise and croissants - but stressed that the move was purely precautionary and that everything possible was being done to eliminate the risks from imported products.
However, a leading British scientist said that the hazards posed by dioxins have been exaggerated, and that the contamination probably poses no significant health risk.
The food scare nevertheless moved into full swing, with consumer groups expressing concern that the contamination might affect more than fresh meat and eggs. Egg powder and pork may have been used in products popular with British shoppers such as Belgian chocolates, pasta, cakes and Ardennes pate.
The Belgian daily newspaper Het Nieuwsblad asked: "What is there left to eat?" It detailed how products ranging from pork chops to egg salad, and mayonnaise to ice cream, had either been taken off shelves or were now under suspicion.
British supermarket chains were yesterday rushing to draw up lists of potentially suspect products in order to trace them back to suppliers to decide if they might have been affected.
The dioxins are understood to have contaminated poultry and pig feed when mineral and industrial oil were mixed at a Belgian animal feed supplier. This was then sold to 416 Belgian farms and exported to France and Holland. Levels of the chemicals were 700 times above normal. However, no British company is thought to have imported the feed.
Yesterday, European Union officials said that Belgian pork might be affected, and in a television interview Belgium's newly-appointed Health minister, Luc van den Bossche, said that the government was also testing beef for possible contamination.
Fresh pork imports from Belgium account for less than 5,000 of the 861,000 tons consumed annually in the UK, though some 3,000 tons of Belgian processed pork and 8,000 tons of liver pate (from either chicken or pork sources) are imported by the UK every year.
On Wednesday, in scenes reminiscent of the panic over the BSE crisis, the European Union ordered all Belgian chicken and eggs exported after 15 January to be destroyed. This move may be extended to pigs, following yesterday's revelations.
That leaves the possibility that consumers in the UK and across Europe have eaten Belgian products contaminated by dioxin over recent months, and that these products could still be on the shelves.
However, the chemist and science writer in residence at Cambridge University, John Emsley, said: "Though you would never want dioxins deliberately added to the food supply, it's important to recognise that no human has ever died directly from dioxin exposure. The only proven symptom is a form of acne, which clears up. Repeated studies have not shown a link with cancer or birth defects.
"If you know that food is contaminated, throw it away. But if you've eaten a Belgian chocolate in the last few months, I wouldn't worry," he said.
THE FEARSOME reputation of dioxins is probably misplaced. Though there are 210 compounds that can be defined as dioxins, only 17 are toxic. The only proven effects of serious exposure on humans is a form of acne. Toxins wereblamed for birth defects after use of the Agent Orange defoliant in Vietnam, and an industrial accident in Seveso, Italy in 1976. John Emsley, science writer-in-residence at Cambridge University, said: "After Seveso a lot of women had abortions because they feared birth defects - but subsequent studies found no long- term increase in birth defects among people exposed."