Government food inspectors have found sulphites in over one third of meat products tested from butchers known to have bought the preservative, even though it is illegal to add the product to meat.

Half the 42 meat processing firms and butchers were found to have used sulphites in their products but none had told their customers, the NVWA said. It is illegal not to mention the presence of sulphites, which are also used to keep red meat red, on packaging or in information to consumers.

In total, the NVWA analysed 134 samples of mince, including hamburgers and steak tartar and found sulphites in 52. All 21 companies found to have used sulphites, which can cause allergic reactions such as hives, were fined.

An NVWA spokesman told broadcaster NOS that the tests had been focused on companies which were thought to present a risk, and so could not be applied across the meat processing sector in general.