Dried oregano is found to be adulterated with other ingredients such as olive and myrtle leaves, according to a study by Belfast Queen’s University's food safety academic Professor Chris Elliott.
Figures released by the study show that around 25% of oregano contains other ingredients that make up around 70% of the product.
As part of the study, Elliott tested 78 samples of dried oregano, from a range of retailers in the UK and Ireland and from online retailers, using mass spectrometry which identifies compounds by their atomic composition.
Elliott said: "Clearly we have identified a major problem and it may well reflect issues with other herbs and spices that enter the British Isles through complex supply chains.
"Much better controls are needed to protect the consumer from purchasing heavily contaminated products."
McCormick Global Quality Assurance corporate vice president Roger Lawrence responded to the study as saying: "We are pleased this issue is getting attention and believe it's important consumers learn all spices and herbs aren't created equal.
"While Professor Elliott's study found as much as 30 to 70 percent non-oregano material in other brands, Schwartz oregano is simply oregano delivering 100 percent pure flavour.
"Our oregano contains no other green leaves like myrtle, cistus and olive."
