The UK Food Standards Agency has issued a warning to consumers over counterfeit bottles of Johnnie Walker Black Label in circulation in the UK which are contaminated with unacceptably high levels of methanol.

Methanol, which should not be present in whisky at any levels, causes severe abdominal pain, drowsiness, dizziness, blurred vision leading to blindness and the risk of coma with breathing difficulties. The statement from the agency says the whisky is counterfeit and should not be consumed.

The Agency was alerted to the problem when a member of the public in London made a complaint to the Johnnie Walker brandowner, Diageo.

"Tests carried out on the counterfeit whisky show that it has been contaminated with methanol," said Andrew Wadge, head of the Agency's Chemical Safety and Toxicology unit. "At these levels detected, consumers would be at risk of harmful effects including severe stomach pain, vomiting and blindness. We strongly advise people to check bottles that they may have at home to ensure that they have the genuine product. The counterfeit product should be avoided and anyone who thinks they may have drunk it within the last 24 hours should contact their doctor."

The counterfeit bottles can be distinguished from genuine Johnnie Walker Black Label whisky in a number of ways. There is Spanish on the rear label, the fake lot code L04P24878342 is printed on the back, the word "Distilleries" rather than "Distillers" appears on the Royal warrant and the counterfeit bottles have no "E mark" on their base between 700ml and 73mm.