Tests carried out by The Daily Telegraph have found vegetarian meals from Tesco and Sainsbury to contain traces of meat.
Following the research the Food Standards Agency (FSA) is to conduct an investigation into the products, one of which passed an independent test by the Vegetarian Society.
The products in question were Sainsbury’s Meat Free Meatballs and Tesco’s Wicked Kitchen BBQ Butternut Mac.
The samples were tested for same paper at a food testing laboratory approved by the German government, while the supermarkets each say they carried out their own tests which found no traces of meat.
An FSA spokesperson said: “Our priority is to ensure consumers can be confident that the food they eat is safe and is what it says it is.
“We are investigating the circumstances surrounding these alleged incidents and any resulting action will depend upon the evidence found.”
A Sainsbury’s spokesperson said: “These products are produced at a meat-free factory.
“Sainsbury’s and the Vegetarian Society also carry out regular checks and no issues have been found.
“We are concerned by these findings however and are carrying out a comprehensive investigation alongside our supplier.”
A Tesco spokesperson said: “We take the quality and integrity of our products extremely seriously and understand that our vegan and vegetarian products should be exactly that.
“Our initial DNA tests have found no traces of animal DNA in the BBQ Butternut Mac product available in stores today.
“We would urge the Telegraph to share full details of their testing, including the lab used, as we continue to investigate.”