Trading Standards chiefs in Hertfordshire are warning residents to be wary of buying counterfeit Glen's Vodka which could cause blindness.

Cheap "knock-off" 70cl bottles of the spirit, which has not been through the company's strict distilling process, has been found at five locations in neighbouring Buckinghamshire.

The discovery has sparked a national investigation.

County councillor Richard Smith, executive member for community safety, said: "There is a possibility that it may be on sale in Hertfordshire too, so businesses and consumers need to take extra care when buying this drink - especially from an unusual source.

"Make sure that you verify the authenticity of the vodka.

"Do not be tempted to buy the cheap version as its strength and effect cannot be certified.

"In past cases, counterfeit vodka has proved to be very dangerous to people's health and can cause blindness and even death."

Genuine Glen's Vodka 70cl can be easily identified.

It comes in bottles supplied by Allied Glass Containers with a small AGC logo on the base.

The following information is also embossed in the glass around 5mm from the base: 70cl 58mm C12173.

Any bottle of Glen's Vodka 70cl without this marking is counterfeit.

Counterfeit bottles found so far have the following codes embossed in the glass: SE607 700ml 66mm, 8509 700ml 66mm, 7828 700ml 66mm.

The front and back labels on the counterfeit bottles appear to be self-adhesive as there is no visible glue pattern.

Anyone who has purchased or been offered cheap Glen's Vodka should contact Consumer Direct, the Government helpline which offers free impartial advice to consumers, on 08454 04 05 06.