21.8% of meat tested by local authorities last year was found to include the DNA of animals not included on its labelling, it has been revealed.
A BBC investigation found that, of 665 meats tested in England, Wales and Northern Ireland in 2017, 145 were found to be partly or wholly made up of other meats.
The number of business implicated totalled 487. Of those 73 were from retailers, 50 came from restaurants and 22 examples were found in food processing plants.
Broken down by type, lamb was the most frequently contaminated meat in the selection, making up 77 (53%) of the cases. 29 cases (20%) were of beef being contaminated while a further 19 (13%) were instances of contaminated goat meat.
In one instance a portion of ostrich was found to have 100% cow DNA. The most commonly misidentified products were mince meat, followed by sausages, kebabs and restaurant curries.
An FSA spokesman said: "These figures are from local authorities who carry out sampling programmes which are designed to focus on specific food businesses types where meat substitution is more likely to occur.
"The number of unsatisfactory samples is a result of this targeted approach where businesses which don't comply are sampled multiple times, and the figures are not representative of the wider food industry.
"Where problems are found, local authorities can consider appropriate action to protect customers and improve compliance, which may include a formal warning or taking enforcement action such as prosecutions or cautions."