Four supermarkets have taken products off their shelves in the wake of the egg contamination scare - as the Food Standards Agency says the scale of the problem is higher than previously thought.

Around 700,000 eggs from Dutch farms implicated in the Fipronil contamination scare have been distributed to Britain, rather than the 21,000 first estimated.

In response, Sainsbury's, Morrisons, Waitrose and Asda have withdrawn a total of 11 products - including sandwiches, sandwich fillers and salads.

The move came as Dutch investigators detained two men suspected of being involved in the illegal use of the pesticide at poultry farms.

The FSA said all products withdrawn in the UK were processed foods in which egg was one ingredient among many others, mostly used in sandwich fillings or other chilled foods.

It said some of the products made from these eggs would have already been consumed, but some were still within the expiry date and were being withdrawn by the businesses involved.

The Food Standard Agency said investigations into the incident suggested it was "very unlikely" that the eggs posed a risk to public health as it released a list of processed products withdrawn in the UK "to ensure that consumers are protected".

FSA chairwoman Heather Hancock said: "I'm confident that acting quickly is the right thing to do.

"The number of eggs involved is small in proportion to the number of eggs we eat, and it is very unlikely that there is a risk to public health.

"Based on the available evidence there is no need for people to change the way they consume or cook eggs. However, Fipronil is not legally allowed for use near food-producing animals and it shouldn't be there."

The FSA said it had no evidence that eggs laid in the UK were contaminated or that Fipronil had been used inappropriately here, and testing results to date for England and Wales showed no exposure to the pesticide.

British egg processors have criticised the buying policies of the UK's major supermarkets after the FSA released the list of withdrawn products.

British Lion Egg Processors chairman Ian Jones said: "The major retailers are operating to double standards when it comes to eggs. All of them stock British Lion shell eggs but they use imported eggs in many of their other foods containing eggs.

"This is just the latest of a number of food safety issues connected to eggs produced outside of the UK in recent years. Consumers clearly want retailers and food manufacturers to use good-quality British ingredients that are produced to high standards of food safety, but in some prepared foods this is not the case."

Britain produces 85per cent of the eggs it consumes but imports almost two billion annually.