By Sean Poulter
Chicken sold in Indian and Chinese restaurants and some cafes is being secretly pumped up with a water and chemical mix containing pork or beef.
The tactic fools customers into thinking they are getting more for their money.
It means consumers are eating beef and pork - generally waste skin harvested from carcasses - without being told.
Scam: Chicken breasts are secretly being injected with pork and beef materials to bulk them up, before being sold on to wholesalers in Britain
The news will alarm the country's two million Muslims, Jews and Hindus, who are forbidden from eating either pork or beef for religious and cultural reasons.
The problem has been highlighted in a study by the Food Standards Agency, which carried out DNA testing of the chemical powders used for bulking up chicken in three production plants - two in the UK and one on the Continent.
The revelations come amid concerns that the Agency has failed to end the food scam it has known about for at least six years.
Chicken breasts can be injected with the water and chemical cocktail or bulked up by placing them in a device similar to a washing machine with the mix.
Alarm: Muslims who eat halal meat from approved butchers may have unwittingly eaten food containing pork (which they are forbidden from eating) in restaurants
Commonly the powder contains salts or phosphates, which helps retain water, together with flavourings, preservatives and sugar.
The study showed that Indian and Chinese restaurants, which often buy cheap chicken in bulk, will see information on the labels about added water and other ingredients.
However, they will not be told about the presence of beef and pork.
False labelling: Jews who also don't eat pork, are at risk in Chinese and Indian restaurants
Chief policy adviser at Which? consumer group, Sue Davies, called for the FSA to take tough action.
She said: 'The findings of this study are shocking. Consumers don't expect to be paying for water or eating beef when they order chicken in a restaurant.'
The Agency said it is considering taking legal action against the UK plants using the chemical cocktail under labelling laws.