Jamie Oliver's butcher's shop temporarily closed after inspectors found serious hygiene problems including mouse droppings and mould on carcasses.
Barbecoa Butchers, near St Paul's Cathedral in the City of London, closed its doors for 24 hours after public health officers scored it one out of five in an inspection in January and said "major improvement was necessary."
A Jamie Oliver Restaurant Group spokeswoman said the "immediate decision" to close was voluntary and not enforced.
Mould was found on carcasses in basement chillers, equipment was left dirty and meat including wagyu beef was out of date, The Times reported after a freedom of information request.
There was a "heavy presence of mouse droppings", inspectors said.
Dirty fridge handles, inadequate washing facilities and damaged floors were also found.
Barbecoa describes the quality of their meat as "second to none".
"We have since continued to receive very positive feedback from the EHO with regards to all improvements and we are confident that the butchery will achieve a high rating in its next inspection," a JO Restaurant Group spokesman said.
"Issues such as this are extremely rare within the JO Restaurant Group and are treated with the utmost severity."