Almost a fifth of foods labelled "local" in England and Wales are making the claim falsely, a study suggests.
Local Government Regulation inspectors tested 558 items in 300 shops, restaurants, markets and factories.
They found misleading labels including "Welsh lamb" which actually came from New Zealand, "Somerset butter" from Scotland and "Devon ham" from Denmark.
The LGR said 18% of the local claims were "undoubtedly false", with a further 14% unverifiable.
The LGR, which oversees council regulation, said it therefore assumed these to be false too.
The survey also found cases where ice cream marketed as local was a well-known brand, "fresh local cream" was a cream substitute containing vegetable fat and "Yorkshire chillies" in sausages were supermarket-bought.
"West Country fish fillets", where fish is caught in the West Country but filleted in China, was another highlighted example.
At 19%, restaurants had the highest incidence of false claims, while manufacturers had the fewest with 11%.
LGR chairman, Councillor Paul Bettison, said the results were "extremely worrying".
"Councils are working with businesses to make sure consumers have the information they need and that they are not being ripped off," he said.
"Many people want to support local businesses or choose food that has not travelled from the other side of the world, so it is vital that they have accurate information to help them make their choices."
There is currently no legal definition of the term "local" in food labelling legislation.
But the Food Law Practice Guidance states local and localised should mean: "Sales within the supplying establishment's own county plus the greater of either the neighbouring county or counties or 30 miles/50 kilometres from the boundary of the supplying establishment's county."