Exposed: the secret ingredient in chicken

Food watchdogs have vowed to clamp down on the sale of chicken which has been injected with beef and pork proteins to schools, restaurants and supermarkets.

Trading Standards officials are horrified that Dutch manufacturers regularly adulterate chicken using beef derivatives.

Brands which are aimed at children, such as Sainsbury's Blue Parrot chicken nuggets, were found to contain the DNA.

An undercover investigation has revealed that producers add the meat proteins so that the chicken absorbs water and fetches more on the open market when it is sold to British wholesalers.

The practice is particularly worrying because manufacturers in Holland claim to have developed a way of adding the proteins without health watchdogs detecting it.

David Walker, spokesman for the Trading Standards Institute, said: "It is clear that some brands of imported frozen chicken meat continue to be adulterated.

"The authorities in the countries in question are fully aware of the nature of the problem. The time for action is long overdue.

"Trading Standards officers will continue to take action against importers who have a moral and legal obligation to check the quality of the food they sell. These issues should be fully addressed by the Food Standards Agency in the proposals for the new meat product regulations.

"Any added proteins and waterenhancing ingredients should be prominently declared in the name of the food."

There are also fears that beef proteins could carry the risk of BSE. However, this risk is thought to be minimal, mainly because the beef used by the Dutch companies is imported from Brazil, which is BSE-free.

In an interview with reporters from BBC's Panorama programme, the head of a German company which extracts the meat proteins claimed that his firm, Prowico, had developed ways of refining them to such a low level that the FSA would not be able to detect them.

Regulations state that it is legal to add beef or proteins to chicken as long as this is explained in clear labelling to consumers.

Tests by the FSA last year revealed that some chicken served in UK restaurants contains beef and pork proteins to help the meat contain up to 50 per cent water.

Companies which have imported the meat into Britain without declaring the additives are facing prosecution and four have already been found guilty of the practice. The Panorama team sent 12 samples of meat bought from Dutch manufacturers to the same laboratory used by British authorities, which found nothing. When the same samples were sent to another laboratory, many were found to contain beef.

Prowico said it declared the contents of the foods it sells and claimed that the new, refined beef protein was not an attempt to mislead customers but simply to make a pure ingredient.

Sainsbury's said that the beef additives in its chicken nuggets could have come from milk also added to the product. "We are entirely satisfied that our supplier is only using chicken suppliers who are approved by us," a spokesman said.