More than a fifth of lamb dishes sold in UK takeaway outlets are adulterated with other meats, Food Standards Agency research has suggested.

Of 307 lamb dishes, such as curries and kebabs, sampled nationwide by local authorities between May and July 2014, some 65 (21%) were found to contain undeclared meat such as beef, chicken, and, in one sample, pork.

While 73% of all meat sampled complied with legislation, a further 4% tested positive for the presence of undeclared allergens – including peanut and almond proteins – with 2% non-compliant because of the unauthorised use of additives.

The results were a slight improvement on an investigation by the food watchdog last year, which revealed almost 30% of tested lamb dishes contained other, undeclared meats, while a separate poll by consumer group Which? suggested as much as 40% of takeaway lamb was contaminated with other species.

Despite the improvement, the FSA warned the ongoing substitution of lamb with cheaper meats remained a problem, and said was working with local authorities to spot deliberate meat substitution.

“Action will be taken to protect local consumers and legitimate food businesses,” said FSA head of local delivery John Barnes, with fines of up to £5,000 imposed on offending retailers if they contravene EU labelling laws.

“Consumers need to know that the food they buy is what it says on the menu or the label”, he said, adding the FSA’s new food crime unit was “working closely” with various agencies “to pool intelligence and take proactive action to protect consumers.”