The veterinary drug phenylbutazone, or bute, has been found in Asda Smart Price corned beef.

The product had already been withdrawn from the shelves after horsemeat above the 1% threshhold was detected last month.

The UK’s Food Standards Agency said the levels of bute were “very low” but urged consumers to return the product to Asda stores rather than consume the corned beef.

The UK arm of Wal-Mart Stores will be placing recall notices in the national press. Asda is also recalling tinned corned beef sold under another private label, Chosen By You, which did not test positive for Bute but was manufactured in the same factory as the Smart Price product.

In a statement, the retailer emphasised there is a “very low health risk” to consumers who have eaten the contaminated corned beef.

“I know our customers will be just as concerned about this news as we are. Even at such a low level, it is totally unacceptable,” Ade McKeon, the Asda director responsible for own-label quality said. “I can reassure our customers that we are working closely with the FSA and our suppliers to deliver a wide ranging and rigorous programme of testing, to be sure that the products we sell are exactly what it says on the label.”

Asda, along with a swathe of other European retailers, introduced a testing programme to detect horsemeat in foods earlier this year after the discovery of unlabelled horse meat in processed foods shook the confidence of European consumers in the food chain.