Subway has said it is bringing an end to its free sandwich promotion amid fears that counterfeiters have been forging the company's proof-of-purchase stamps and cards.
The Sub Club promotion, which has been running in some form since the 1980s, gave customers a stamp for each sandwich they bought. Eight stamps could be exchanged for a free sandwich.
However, the company said franchise owners were increasingly discovering counterfeit stamps and internet sites were offering stamps for sale.
Kevin Kane, spokesman for the company, said: "It's possible some of the stamps got by and we don't even know. It's possible we don't even know the extent of it."
Every Subway store has until 1 October to phase out the promotion.
