Supermarket giant Asda has been fined £300,000 after dead mice were found in a London depot.
Shocking images from the storage facility in Enfield showed dead mice on the floor.
The depot is used as a base from which food is delivered to online shoppers across the capital.
Food safety officers from Enfield Council made the gruesome discovery during a visit to the site in Southbury Road.
Officers found dead mice and flies in the bread section, mouse droppings on shelves and packets of cereal and sugar which had been gnawed by rodents on the home baking aisle.
They also found fly pupae shells under shelves, spilt food stuffs and rotting coriander in home delivery trays.
Enfield Council’s Cabinet Member for Environment, Cllr Daniel Anderson, described the situation as "simply unacceptable".
He said: “It beggars belief that a national retailer would allow food to be stored in an environment where rodents are running riot.
“It is simply unacceptable for customers to be exposed to the potential risk of harm because a company cannot get its house in order and store foodstuff in a safe and hygienic manner.”
Asda pleaded guilty to three breaches of the Food Safety and Hygiene Regulations at Highbury Corner Magistrates' Court in January following the visit in May last year.
The company was sentenced at the same court on Friday, and ordered to pay costs of £4,843.61 to Enfield Council.
Cllr Anderson added: “I am pleased that magistrates have taken a tough stance and issued a heavy penalty.
"Hopefully it will send out a strong message to all retailers that we will not tolerate them being less than properly vigilant and ensuring their staff abide by their own stated hygiene policies to protect the health and wellbeing of their customers."
An Asda spokesman said: “The conditions found at our Enfield home shopping centre in May 2016 were completely unacceptable and we are deeply sorry that on this occasion the strict processes we have in place failed at a local level.
"We would like to reassure all our customers that immediate steps were taken as soon as the issue was flagged last year to restore the high standards that our customers expect from us.”