The Consorzio del Prosciutto di Parma, the powerful Parma ham trade association, had complained that the Asda product was not genuine because it was sliced and packaged in the West Country.
According to Italian law, the ham must be fully prepared for sale in the Parma region of the Po Valley under the control of the Consorzio, which has police-like powers to enforce compliance with the rules. But deputy judge Lawrence Collins QC refused to grant the Consorzio an injunction banning Asda from selling its genuine Parma ham simply because it was sliced and packed in England.
He ruled that although EU regulations gave Parma a protected "designation of origin", they did not include the strict Italian rules on slicing and packaging.
Asda said it was ridiculous to suggest that its ham was somehow inferior because of where it had been packed. "Whether we slice our ham in Parma, Pudsey, Plymouth or Perth is completely irrelevant," said Asda's marketing director Steven Cain.
The ruling angered the Italians, who have been granted leave to appeal. Their solicitor, Arturo Barone, said after the hearing that the judge's decision had serious implications for the producers of many other products protected by designation of origin.
Parma ham, he said, was a very fine delicacy, and its reputation and quality depended on the rigorous controls operated by the producers. His clients would seek to take the case to the European Court of Justice if necessary.
The EU suggested yesterday that the Italians had a good case. Its spokesman, Gerry Kiely, said: "I would agree that just because it is sliced at the point of retail doesn't mean it's of inferior quality but nevertheless we consider that whoever registered the name has the right to determine how it is treated at the point of retail. This reduces the possibility of the consumer being misled."
Ham has been produced in the Po Valley for more than 2,000 years. The Parma hills are ideal for curing hams because of their low humidity. There are 5,600 recognised pig breeders and 220 slaughterers. Detailed laws regulate the type of pigs used, their rearing conditions, diet and slaughtering procedures.
Parma hams were matured for 10 or 12 months and bore the distinctive Ducal Crown mark. Since the 1980s, the Consorzio had launched 300 sets of legal proceedings outside Italy to protect the interests of its members in the integrity and name of the product.
After the case, the supermarket chain, which undercuts its nearest competitor's prices by 25 per cent, celebrated its legal victory by setting up a Parma ham stall on the pavement outside the High Court in London.
Last March, Asda supermarket staff had dressed up in Puffin and Penguin outfits to protest at a case brought against it by United Biscuits. The judge found Asda guilty of passing off its brand of chocolate biscuit, called Puffin, as the famous Penguin.Reuse content