Six lorryloads of turkey meat sent to Hungary last week from the Bernard Matthews plant at the centre of the avian flu outbreak were raw and may have returned the H5N1 virus to Central Europe.

The revelation immediately sparked a political and diplomatic row between London and Budapest. Miklos Suth, the Hungarian chief vet, said that he was outraged by the consignment of raw meat from an infected zone.

Poultry industry chiefs and farmers were incensed by the move and believed that it would lead to a collapse of consumer confidence in all turkey and chicken, especially as the route of the infection from Hungary to Suffolk has still not been established.

The news came as it was confirmed last night that Bernard Matthews had been given permission to reopen the abattoir part of his processing unit at Holton, Suffolk, where 160,000 birds were culled to halt the spread of the disease a week ago. Supermarkets report that the biggest loss in sales is for Bernard Matthews branded products and buyers are privately reporting to industry sources a drop of 50 per cent in the company’s products. Other poultry sales are 10 per cent down.

There also appears to be a North-South divide over the scare: many more shoppers in London and the South East are shunning Bernard Matthews meat than those in the North East and North West.

The Food Standards Agency is still searching documents and meat held in cold stores to check whether any possible infected meat has entered the food chain.

The conduct of Bernard Matthews itself is under increasing scrutiny. One Whitehall official described “quiet rage” over delays by the company in handing over transport documents listing the consignments that have travelled between Britain and Hungary. It took three days for the company to accede to requests for information.

A senior executive at the company had told ministers that meat from Hungary came only from the Sarkov plant, more than 100 miles away from the restricted zone. It was a government meat-hygiene inspector who spotted a label revealing that meat had come from an abattoir in Kecskemet, just outside the H5N1 zone.

There was disbelief in farming circles that the meat exported to Hungary last week was raw. A European Commission spokesman said that it was legal to send raw meat to Hungary provided that the product did not come from poultry slaughtered in the protection zone around an outbreak; that the meat was processed and packed separately; and that it had been held in separate cold storage.

Chris Huhne, the Liberal Democrat rural affairs spokesman, said, however, that even if it was allowed within the letter of the law, “Such a move was unwise and I can understand why the Hungarians are hopping mad about it, especially when the source of infection is still unknown”.

For the past 24 hours government officials defended the exports because the meat was cooked and therefore of minimal risk of spreading the virus. Mr Suth confirmed, however, that the meat was raw and that the Holton plant exported only raw, processed turkey meat, which is used for the production of sausages at the SaGa Foods Sarkov plant. These products are then distributed in Hungary, Germany and Italy.

A meeting between David Miliband, the Environment Secretary, and Borbala Czako, the Hungarian Ambassador to London, was arranged hastily yesterday in an attempt to repair cooperation between the two EU member states. Mr Miliband also telephoned his Hungarian counterpart, Jozsef Graf, and Mr Suth.

A spokesman for the Department for Environment, Food and Rural Affairs would not comment directly about the raw meat assertion and said that the matter was under investigation. Another official had previously said that there was no risk from cooked meat that had left the Bernard Matthews farm. “The heating process quickly kills the virus and therefore this meat will be perfectly safe,” she said.

Mr Miliband toured tele-vision studios to defend the containment of the outbreak and the investigations into the source of the infection.

The British authorities were informed yesterday that checks by the Hungarians on the movement of meat from last November had shown that no poultry from the Csongrad region, at the centre of the H5N1 outbreak, had been sent to abattoirs used by Bernard Matthews at Sarkov or Kecskemet.

Scientific and veterinary experts in Brussels also believe that there is no evidence that turkeys in Hungary are infected with the virus, and believe that the most likely source of contamination in Britain is the movement of people, vehicles, packaging or equipment. Transmission by wild birds also remains a possibility.

A spokesman for Markos Kyprianou, EC Health Commissioner, said the source may never be established.

A veterinary report on the precise match of the lethal avian flu strain is to be published in Brussels today and an epidemiological report into the investigation in Britain on Friday. A review of the EU rules on the trade and movement of poultry from countries with an outbreak of H5N1 is inevitable.

There is also considerable confusion about the rules. A Brussels spokesman said that the export of raw processed meat “in principle may not cause a problem provided it was processed and packed separately from any meat from poultry slaughtered in a protection zone”.

It is not clear if there is a cooking facility at the Bernard Matthews Holton plant. A company spokesman was unable to give the information to The Times yesterday.

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