Walkers Crisps have promised that new meat flavouring in its previous vegetarian-friendly signature crisps, will be clearly labelled.

Currently, Walkers’ salted, salt and shake, and salt and vinegar crisps are certified kosher by the London Beth Din.

Other varieties, such as roast chicken, smoky bacon or cheese and onion, do not have hechshers but have long been considered vegetarian-friendly, containing chemical flavouring rather than real meat or cheese.

But, in a move fiercely condemned by vegetarians, Walkers has now announced that these flavours will “include delicious home-grown ingredients...”, and will no longer be suitable for non meat-eaters.

A spokeswoman said that the crisp packets would denote the change in ingredients. But Rabbi Jeremy Conway, executive director of the London Beth Din kashrut division, said the development highlighted “the importance of checking that a product is listed as approved before buying.

“This is the only way that one can be absolutely certain about the provenance of a food item.”