The Food Standards Agency has told Channel 4 News that UK horse meat contaminated with a toxic drug was consumed in France before it could be recalled.
The revelation comes after shadow environment secretary Mary Creagh told the Commons she had evidence that "several" horses slaughtered in the UK last year tested positive for the carcinogen phenylbutazone, aslo known as bute.
Her claim, that this meat may have entered the food chain, follows the discovery that burgers in some supermarkets contained traces of horse meat.
The Food Standards Agency (FSA) told Channel 4 News that the contamination was identified by its routine inspections in eight samples of horse meat, five were exported to France. It also confirmed this evening that all the meat had been consumed by the time French authorities were notified.
Science Editor Tom Clarke writes:
So how worried should French people be that British horsemeat containing phenylbutazone was sold to them as safe?
Well when it comes to the immediate health risk,they shouldn't worry at all. Phenylbutazone was a drug developed to treat athritis in humans. At high doses it sometimes caused a rare disorder called blood dyscasias by killing cells in the bone marrow. As a result it was banned as a drug in humans. Just to be extra safe a decision was made to add it to a list of drugs that should not be given to animals destined for human consumption.
But even if a horse was given high doses of the drug, by the time it ends up in a meat product, the dose to a person - which is only likely to be a one-off dose - would be very small. Prof Sir Colin Berry, a veteran pathologist at Queen Mary, University of London, said: “The compound has rarely caused blood dyscrasias even on those who have taken a lot for many years. The idea that you might get a clinically significant amount in horse meat even after therapeutic administration to the horse is, frankly, daft.”
But this doesn't mean there's not cause for concern. A European-wide horse passport system is designed to record things like medicines given to horses. Information which should be known to the two abatoirs in the UK which slaughter horses for meat. A horse that has been given the drug shouldn't end up at a slaughterhouse, let alone on somone's dinner table.
The fact that a horses containing this drug were sold for huamn consumption raises important questions about how seriously horse owners and slaughterhouses take rules designed to keep us all safe.
Ms Creagh said: "I am in receipt of evidence showing that several horses slaughtered in UK abattoirs last year tested positive for phenylbutazone, or bute, a drug which causes cancer in humans and is banned from the human food chain.
"It is possible that those animals entered the human food chain."
"I am astonished you have not raised this and I think the public have a right to know," she added.
Read more - Horse meat burgers: the key questions
She also questioned the government's "short-sighted and reckless decision" to shut the National Equine Database (NED) in August last year. The NED was the UK's only database of all UK horses.
Agriculture minister David Heath replied that the Food Standards Agency (FSA) checked all meat to ensure it was fit for human consumption, saying: "The Food Standards Agency carry out checks in slaughterhouses to ensure that equine animals presented for slaughter are fit for human consumption in the same way as they do for cattle, sheep and other animals.
"In addition, the FSA carry out subsequent testing for phenylbutazone and other veterinary medicines in meat from horses slaughtered in this country.
"Where positive results for phenylbutazone are found, the FSA investigates and takes follow-up action to trace the meat."
He also said that it appeared Ms Creagh did not understand what the role of the NED had been, and said there is "no difficulty" in tracing details about horses.
The FSA issued the following statement after the comments in the House of Commons on Thursday.
"In 2012, the FSA identified eight cases where horses tested positive for bute. Five were exported for the food chain. None of the meat was destined for the UK.
"Where the meat had been exported to other countries, the relevant food safety authorities were informed. The other three did not enter the food chain. None of the meat had been placed for sale on the UK market.
"Horses that have been treated with the drug phenylbutazone or 'bute' are not allowed to enter the food chain. The Food Standards Agency (FSA) carries out checks in slaughterhouses to ensure that horses presented for slaughter are fit for human consumption, in the same was as they do for other animals such as sheep and cattle. The FSA also carries out regular enhanced sampling and testing for phenylbutazone in meat from horses slaughtered in the UK.
"During the recent horsemeat incident the Food Safety Authority of Ireland checked for the presence of phenylbutazone and the samples came back negative."
The discovery of traces of horse meat in burgers being sold by Tesco and other supermarkets led to ten million burgers being taken off shelves across the UK and Ireland.
Irish firm Silvercrest Foods recalled the burgers after horse DNA was found in some of its beef products. On Thursday, Burger King said it had dropped Silvercrest as its supplier as a "precautionary measure".
Ingredients suppliers in the Netherlands and Spain have been identified as the possible sources for incorrectly labelled ingredients.
Please wait while this video loads. If it doesn't load after a few seconds you may need to have Adobe Flash installed.