Norfolk Meat Traders, near Banham, had its licence suspended by the Food Standards Agency in April while it investigated the alleged unauthorised killing of horses at its site at Moor Farm.
But the company went to Great Yarmouth Magistrates Court last week to appeal against the suspension.
Norfolk Meat Traders, which does not have approval to kill horses, argued it had permission to carry out the slaughter on March 31 because it was done on behalf of a company called Zoo Food People which does have a licence.
But the director of Zoo Food People Stephen Toth said he did not authorise the slaughter.
He told the court he had called it off the day before and was not present when the horses were killed.
Director of Norfolk Meat Traders Deborah Wilson told the court she did not know why Mr Toth was not there.
But the court heard she had previously told two people, including the FSA, that Mr Toth was ill so would not be present.
However the court was told Mr Toth was not ill and when he said the killing was not authorised by Zoo Food People, the FSA started an investigation.
An FSA vet said they had not given Norfolk Meat Traders full approval, which would have allowed them to kill horses, because they had concerns about animal welfare at the slaughterhouse.
Rejecting the appeal, magistrates said Miss Wilson deliberately attempted to mislead the FSA to believe she was acting on behalf of Zoo Food People.
Magistrates said Norfolk Meat Traders breaching the terms of its approval and misleading the FSA were “very serious matters”.
Magistrates said they were “in no doubt” it would be “wholly inappropriate” to grant full approval to Norfolk Meat Traders.
A spokesman for the FSA said: “As this case demonstrates, the Food Standards Agency will take appropriate action against any businesses and individuals who breach the strict rules that should be followed in all approved slaughterhouses.”
Their investigation is ongoing.
Eastern Daily Press