The newspaper reported that Lilly-Mae Russell began fighting for breath after she tried to swallow a piece of yellow plastic that had been baked into the muffin.
Lidl has since reassured customers that they are treating the issue as an isolated incident, the newspaper reported, and an investigation is underway to discover the source of the plastic.
A Lidl spokeswoman said: “We are currently speaking with the supplier of the product and have requested that the customer send the object to us for analysis. Once the foreign body has been received by our quality assurance team, typically investigations take seven to 10 working days. We are taking the issue very seriously and will continue to update the customer with any findings.”