Jamie Oliver's exclusive butcher's shop temporarily closed after inspectors found serious hygiene problems including mouse droppings, mould on carcasses and out-of-date meat.
Barbecoa Butchers, located near St Paul's Cathedral in the City of London, closed its doors for several hours after public health officers scored it one out of five in January, although a Jamie Oliver Restaurant Group spokeswoman said the closure was voluntary and not enforced.
It reopened within 24 hours after the issue was addressed.
The Food Standards Agency website lists the score for the January 8 inspection with the comment "major improvement necessary".
Carcasses hanging in basement chillers were found to have mould growing on them, slicers and vacuum packers were left dirty and expensive wagyu beef, marrow bone, oxtail, onglet, and lomo de cana, a Spanish-style pork, was found to be out of date, The Times reported.
In one case chicken breasts which had been deboned were removed from their box, vacuum packed and relabelled with a date set for a week later, City of London inspectors said. There was no safety management system in place.
The butcher's shop, which supplies meat for the restaurant upstairs of the same name, was found to have dirty fridge door handles, inadequate washing facilities for staff, poor lighting, damaged flooring and a "heavy presence" of mouse droppings.
The Times said it used a freedom of information request to obtain details of the extent of the hygiene problems.
The JO Restaurant Group said dry ageing of meat on the bone encourages the natural formation of mould and is common practice in butcheries.
The restaurant was founded in 2010 by Oliver and an American chef, Adam Perry Lang, and its website says the quality of meat in the butchery is "second to none".
The food has received largely positive reviews and its own health inspections have all been good.
A spokeswoman for the JO Restaurant Group said: "Following the environmental health inspection in January we took the immediate decision to voluntarily close the butchery for several hours in order to urgently address the issues raised.
"We reopened within 24 hours and the environmental health officer (EHO) noted that the improvements had been made.
"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.
"Issues such as this are extremely rare within the JO Restaurant Group and are treated with the utmost severity."