The problem came to light after two customers at an Asda branch in Accrington returned bottles of the brand bought from the shop.
Diageo has taken samples from the same batch from the store for testing.
A Diageo spokeswoman said: “We are currently working with Asda to investigate this consumer complaint. We take all complaints very seriously and are in communication with both Asda and the consumers concerned about the matter.”?Asda said it was investigating the claims but was referring enquiries to Diageo as the Smirnoff brand owner.
An Asda spokeswoman said: “Unfortunately, the bottle posted for testing got smashed in transit.”