A Tesco store in Northamptonshire has been fined £14,000 after an "infestation" of mice was found.
Environmental health officers made the discovery in May 2005, after a tip-off from a worker at a store in Kettering, the town's magistrates heard.
The officers found mice droppings and that the animals had gnawed through about 15 bags of crisps at the store.
Tesco, which admitted selling food unfit for human consumption, apologised for the incident.
The company was also ordered to pay costs of £5,300.
The court heard that environmental health officers found an "infestation" of mice.
The officers also found mice droppings in bags of crisps.
A mouse was seen scurrying along the store floor and a nest containing a dead mouse was also found, the court heard.
Lawyers for Tesco said they had employed Rentokil to visit all its outlets.
In a statement, a Tesco spokesperson said: "We are sorry about what happened - this relates to an incident in May 2005.
"We do have robust procedures in place to stop this type of thing from happening but clearly on this occasion it appears we fell well below our usual high standards.
"We have done refresher training with staff in store."