A mislabelled sandwich sold to a customer at a Weymouth supermarket could have triggered a fatal allergic reaction, it is claimed.

Morrisons said it 'deeply regrets' the error and will be reviewing procedures after a member of staff put an incorrect label on the pitta bread product.

Instead of tuna as the label said it contained avocado and egg which could have caused harm to the customer.

Marina Delaney bought two sandwiches from the Weymouth branch of Morrisons in Dorchester Road.

One of them, which was for her sister Marie, was sold as a ‘Mediterranean Style Tuna Pitta Bread’ and had been reduced in price.

When she opened it, however, it turned out that the food had been mislabelled and the pitta bread contained avocado and egg.

Her sister is allergic to avocado, and if she had eaten it, Marina says Marie could have had a fatal allergic reaction.

The sisters had been staying at their holiday home in Weymouth when they visited Morrisons to grab something to eat.

Miss Delaney said: “We are both struggling to deal with what would have happened if she had even put that sandwich to her mouth, as allergic reactions are generally immediate which they are in her case.”

She made the discovery when she opened the packet while they were in their car.

Miss Delaney was forced to clean out the car thoroughly afterwards, as even the touch of avocado could have set off a reaction.

She also commented that the mislabelled food could have caused serious problems to people who have egg allergies as well.

Miss Delaney said: “The obvious thing now is that we both feel scared now about products that we purchase as that trust has been damaged especially with such a big company.

“We feel that everyone should be made aware of the risk that Morrisons exposed to us and others customers.

“Customers should be confident and feel safe that the product they buy is the product advertised.

“The duty of care has been unforgivingly compromised.

"For anyone that has serious allergies, an error like this could be fatal or have life changing consequences.”

A spokesman for Morrisons said: "We take all food safety and quality issues very seriously, including accurate labelling of our products.

"We deeply regret that our customer received the wrong information about the product's contents.

"It would appear a colleague has mistakenly applied an incorrect label.

"We will be be reviewing our procedures and retraining colleagues where appropriate."

Anyone looking for more information regarding food allergies can find it at nhs.uk/conditions/food-allergy