Shoppers have been warned not to buy or eat fake and potentially unsafe Prime or Wonka chocolate bars.
The Food Standards Agency (FSA) said it had received reports of fake branded chocolate on sale and was working with Trading Standards to protect consumers.
Prime, the popular drinks brand, does not make any Prime-branded food products, meaning the chocolate bars are fake and could be unsafe.
The FSA also said any Wonka bars sold in a shop, online or on a market stall “will not be the real thing”.
It warned the ingredients list might not be correct and allergen labels may not have been applied correctly.
Fake Wonka Bars were removed from sale last year after having been found to contain allergens that were not listed on the label, posing a major health risk to anyone who suffers from a food allergy or intolerance.
Tina Potter, head of incidents at the FSA, said: “With Christmas coming up, don’t waste your money on fake branded chocolate for your children, friends or family – you won’t be getting what you think you are paying for and you don’t know what is in them.
“There could be a food safety risk, especially for those with food intolerances or allergies.”
He added: “We know there is a problem with potentially unsafe fake chocolate bars such as Wonka and Prime bars and we’re working with Trading Standards to protect consumers.
“Please do not buy or eat these bars and if you think you’ve bought a fake chocolate bar, or if you see something that does not seem right when you are shopping, report it to your Local Authority.”
The warning follows quantities of hallucinogenic drugs found in “a small number” of chocolate bars sold at Mansfield Market in Nottinghamshire late last month.
Nottinghamshire Police received reports of people falling ill after consuming chocolate both labelled as Cali-Gold and unbranded, and later said Psilocin – found in magic mushrooms – and THC – a substance found in cannabis – were discovered in some of the bars.