A number of restaurants listed on Just Eat, the biggest online food delivery app in the UK, have been found to sell food that could cause allergic reactions, an investigation has found.

More than 100 restaurants on Just Eat, the food ordering app, were also found to have hygiene ratings of zero, despite some being promoted by the app as the “crème de la crème” of takeaways in a particular area.

BBC Panorama investigated a number of restaurants, finding discrepancies in what they were serving compared to what they told customers.

One restaurant was unable to provide even basic, legally required, allergen information when asked by the reporter.

All food businesses are legally required to provide information about 14 major allergens, which includes being able to tell customers whether a meal contains nuts, dairy, gluten, or wheat – all which can be life threatening.

But Just Eat doesn’t require restaurants to provide any allergen information on their app or website. Customers are expected to contact the restaurants directly to find out if a meal is suitable to eat.

A restaurant contacted by BBC Panorama in Greater Manchester, Tong Feng House, had five-star customer reviews on Just Eat but research showed it also had a hygiene rating of zero from the Food Standards Agency.

An undercover Panorama reporter was assured by a Tong Feng House employee over the phone that the chicken chow mein did not contain any wheat. This is an ingredient that can cause allergic reactions, most commonly among children, and which can be severe. However, the meal was collected and sent for testing, revealing that it had a high wheat content.

Tong Feng House told the programme a new staff member provided the incorrect information and they are retraining their team.

A restaurant in Birmingham, Mama Mia Pizza, which was also found to have a zero hygiene rating, sold a burger to a reporter that they said did not contain any wheat. Testing showed it contained gluten, a general name for the proteins found in wheat, which can cause a reaction among allergy sufferers.

Just Eat have launched an investigation, and said it was concerned to discover restaurants were not providing accurate information. “We have already offered further support and training,” it added.

The app also listed more than 100 takeaways with zero hygiene ratings and some were promoted or labelled as a “local legend” to consumers. This title is reserved for the “crème de la crème” of takeaways in a particular area, according to Just Eat. Only restaurants with the highest food hygiene ratings are supposed to be given this title.

Just Eat removed “local legend” status from Karo’s Pizza in Liverpool when it was brought to their attention that the restaurant had a zero rating for hygiene.

The company told Panorama: “We are investigating how this has happened to stop this from happening again.”

Shirley Cramer CBE, the chief executive of the Royal Society for Public Health, said: “The food hygiene rating system is vastly important for us understanding how good a restaurant is.

“I don’t think in anybody’s mind [a zero-rated restaurant] would be a local legend.”