Jamie Oliver temporarily closed the onsite butcher of his City of London restaurant Barbecoa after public health officers scored it one out of five in January.
Inspectors found mouse droppings, out-of-date meat, damaged flooring, unclean fridge door handles, inadequate washing facilities for staff and poor lighting at the site, located behind St Paul's Cathedral.
The findings prompted JO Restaurant Group to close the butchery voluntarily to make necessary improvements, and it was reopened the following day.
A spokeswoman for the company said: "Following the EHO 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 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."
The report also noted mould on the carcasses hanging in basement chillers, according to the Times, however the spokeswoman said this did not make it unfit for human consumption.
They said: "The dry ageing of meat on the bone encourages the natural formation of mould and this is common practise in butcheries.
"The longer the meat dry-ages, the more the mould occurs. This is a natural process and is safe to eat."
She went on to say that instances of this nature are "extremely rare" within the company and are treated with the "upmost severity".
"The group has a Primary Authority Partnership, regulated under the government's Better Regulation Delivery Office (BRDO) which shows our recognition and commitment to maintaining high food safety standards throughout the business," she added.
The Barbecoa restaurant, founded in 2010 by Oliver and American chef Adam Lang, remained open.