Buyers of Asian jewellery in Birmingham have been advised to be cautious about the quality of gold items.
Birmingham City Council trading standards found some items have been sold without a hallmark and marketed with the incorrect carat value.
It visited jewellers in the area to check the origins of their products.
Without a hallmark, customers have no real way of knowing the precious metal content of the item, the authority said.
It added that gold from the Asian sub-continent was not subject to the same hallmarking system as in the UK, but once the item was put on sale in this country, it became subject to the same regulations.
Chris Neville, head of trading standards at the council, said: "People should refuse to buy items that are not hallmarked, as the seller is acting illegally and the hallmark is really the only assurance they have."