More than 20 per cent of lamb takeaway meals contain other types of meat, according to a survey by the Foods Standards Agency (FSA).
Local authority trading standards and environmental health officers sampled 307 lamb dishes, such as curries and kebabs, sold from takeaway outlets across the UK last year.
They were tested for the presence of undeclared species of meat. Dishes with sauces were also tested for undeclared allergens and the unauthorised use of additives.
The FSA said 73 per cent were fully compliant with food legislation, but 21 per cent failed because of the presence of non-declared meat.
The survey found 4 per cent tested positive for the presence of undeclared allergens, including peanut and almond proteins and 2 per cent were non-compliant because of the unauthorised use of additives.
The 65 samples that tested positive for undeclared meat showed the presence of beef, chicken, and in one sample pork, although it had not been sold as a halal product.
Of these samples, 23 had levels of undeclared meat below 1 per cent, which is more likely to be the result of poor handling during processing rather than adulteration, the agency said.
Although the levels of undeclared allergens were indicative of low level cross-contamination from the ingredients or from the kitchen during preparation, they were high enough to cause an allergic reaction, the agency concluded. The testing was prompted by evidence of ongoing substitution of lamb for cheaper meats.
John Barnes, head of local delivery at the FSA, said: “Where problems are identified, local authorities are taking corrective action, including prosecuting offending businesses where necessary.
“The FSA and local authorities are on the lookout for deliberate meat substitution and action will be taken to protect local consumers and legitimate food businesses.”
The FSA's work to identify potential food fraud is being coordinated by the recently created Food Crime Unit. Since December, new legislation has required food businesses to provide allergy information on food sold unpackaged in catering outlets, such as takeaway restaurants. Allergen guidance for businesses is available on the FSA website.