Eggs contaminated with the insecticide fipronil have been discovered in 40 countries, including 24 of the European Union's 28 member states.

Millions of eggs have been pulled from European supermarket shelves, though some national regulators have voiced concern that many contaminated eggs have already entered the food chain, mainly through processed products such as biscuits, cakes and salads.

EU agriculture ministers meeting in Tallinn, Estonia, are due to discuss the egg scandal on Tuesday.

A spokeswoman for the European Commission confirmed that the only EU member states so far unaffected are Lithuania, Portugal, Cyprus and Croatia.

The non-EU states in which contaminated eggs have been discovered include the United States, Russia, South Africa and Turkey.

Authorities in Belgium and The Netherlands traced the source of the insecticide to a supplier of cleaning products. Two Dutch men who ran the cleaning company ‘Chickfriend’ were arrested last month.

Fipronil is considered moderately toxic and can cause organ damage in humans, however, a large number of contaminated eggs would need to be eaten to affect health

The insecticide is widely used to treat pets for ticks and fleas but its use in the food chain - like to clean out barns - is forbidden.