UK Agriculture Minister Nick Brown said he would not eat any of the products, which may have remained on sale in recent days.

He admitted authorities had not acted as quickly as they could have to prevent any risk to consumers.

The BBC's Robert Pigott: "Two Belgian Ministers have resigned over the scandal"

The discovery of a cancer-causing chemical dioxin in feed for hens and pigs on some Belgian farms has already caused two government ministers in that country to quit.

The health scare led the UK Ministry of Agriculture to warn food sellers in Britain to stop using all Belgian chicken, eggs and pork products.

Nick Brown: The UK could have acted quicker to get products off the shelves

Mr Brown said: "My concern is that we've probably got to this later than we should have done."

He agreed this meant some shoppers had probably bought infected products in the past couple of days.

"I'm afraid that's true. Although we believe the level of exposure isn't sufficient to pose any risk to human health it shouldn't have happened at all."

UK Agriculture Minister Nick Brown: "This is a real issue"

The only way to guarantee not being at risk from eggs, poultry or pork from Belgium would be not to eat it, he said, adding, "I wouldn't."

"This is a real issue and there are contaminated products, eggs, poultry products sourced from Belgium that have to be taken off the shelves.

"We've been in touch with the major retailers and asked them to check the sources of their products and if they're sourced from one of the producers who've used contaminated food stuffs the products are to be withdrawn."

Mr Brown said only relatively small quantities of the products were likely to have been imported into the United Kingdom.

A German food chemist tests Belgian eggs for dioxin

The Asda supermarket chain had already said it had withdrawn stocks of three own-brand pre-packed meats over the weekend after preliminary checks.

A spokesman said that while there was no evidence that its Garlic and Herb Chicken, Belgian Chargrilled Chicken and Honey Roast Chicken were affected by the scare, the chain was withdrawing them as a "purely precautionary measure".

Tesco, Sainsbury's and Safeway said they were monitoring the situation and did not believe that any of their products were affected by the scare.

Fast food chain Kentucky Fried Chicken also revealed on Thursday it had halted imports of chicken from Belgium a week ago.

The BBC's Robert Pigott: "We have an almost instinctive suspicion about food now"

"We were contacted by our Belgian operations on Thursday," a spokesman said. "At this point we had not heard from the Ministry of Agriculture.

"This product would have already passed through our system but regardless we took the precaution of halting all imports from Belgium and any stock already held from Belgium was stopped."

France, Germany and the Netherlands are believed to be most at risk from having imported infected animal feed or products.

European Union vets have already ordered the destruction of millions of pounds worth of chicken and eggs products exported from Belgium since 15 January.

The European Commission is expected to take further action on Thursday to protect consumers.