Counterfeiters have been targeting independents in a highly sophisticated scam involving fake bottles of Britain's biggest-selling value vodka brand Glen's.

Counterfeit bottles of Glen's vodka have been found on sale by 24 local authorities in England, four in Scotland and one in Wales.

Brand owner Glen Catrine said it would seek prosecutions where retailers have been knowingly selling the counterfeit vodka.

"It's extremely detrimental to our reputation," said Tom Taylor, quality manager of Glen Catrine. "There's no threat to health, but it is a pretty ropey spirit. It's tending to be picked up in local shops, two or three bottles at a time."

The fake Glen's contains higher than normal levels of methanol, although the FSA said it was unlikely to be a risk to health.

The fraudsters involved had invested significantly in the scam, he added, as they had gone to the lengths of printing "pretty good" labels and caps. Genuine bottles of Glen's can be easily identified by the AGC logo of manufacturer Allied Glass Containers on the base. Bottles also have the code '70cl 58mm C12173' embossed on the glass, around 5mm from the foot of the bottle. Fake bottles have so far been found with the codes 'SE607 700ml 66mm', '808 700ml 66mm' and '7828 700ml 66mm'.

Retailers and consumers have been advised to report suspect stock to Trading Standards or make a report through the food fraud mailbox on the FSA website.