Three supermarket chains have given confusing or incorrect information on potentially lethal food allergens in their bakeries, the BBC has found.
Branches of Asda, Sainsbury's and Tesco gave wrong or unclear details to Watchdog Live's undercover reporters.
It comes after a 15-year-old girl died after eating a baguette from Pret A Manger, which did not specify the presence of sesame in the sandwich.
The retailers said they would review their labelling and staff training.
Undercover reporters for the BBC's consumer programme visited 24 supermarket bakeries, five of which showed cause for concern.
The EU says that consumers must be made aware when one or more of 14 particular allergens – including nuts, sesame, milk, eggs and wheat – is used as an ingredient in food products.
However, in the UK freshly handmade non pre-packaged food does not need to be individually labelled on packaging, but stores must ensure clear and accurate information is readily available.
But that is not always the case, the programme found.
In one Asda bakery, staff said an item did not contain the allergen sesame, when it was in fact listed as an ingredient for the product on the store's website.
In other Asda stores, the programme found staff were able to give a general warning that products may contain nuts or seeds, without being able to identify specific allergens contained within the recipe.
The sesame allergy that killed a teenager
In September a coroner ruled that sandwich chain Pret A Manger's labelling was inadequate, after a girl suffered a cardiac arrest after eating one of its baguettes.
Natasha Ednan-Laperouse visited the Heathrow Airport branch in 2016 before getting a flight with her family.
Despite having two EpiPen injections while on the flight, the teenager died in a hospital in Nice.
Natasha's family said food labelling laws "played Russian roulette with our daughter's life".
Since then the sandwich chain has said it will list all ingredients, including allergens on its freshly made products.
Reporters for the programme found Tesco did list allergens on most of its products, but not for unwrapped bread rolls, paninis and pastries in some stores.
At one branch, an undercover reporter posing as someone with a milk allergy found a senior member of staff who was unable to locate any ingredients information for an unpackaged panini that contained milk.
Sainsbury's did not list any of the 14 allergens on packaging or shelf labels in their in-store bakeries, but did tell customers to "ask a bakery colleague" about allergens.
A staff member at one branch told an undercover reporter a raisin whirl was free of nuts – but when the staff member found a product information guide it listed almonds as an ingredient.
Sainsbury's said it would update its labels "to include more specific allergen information".
Tesco said it exceeded "the current legal requirements", but in light of the Watchdog investigation a spokesperson said the food retailer would be "reviewing how allergy information is displayed moving forward".
Asda said in all the instances flagged up by Watchdog Live, its staff "ultimately advised the customer not to buy the product".
But a spokesman added the supermarket was "also working to implement detailed allergen labels on our in-store bakery products".