According to an investigation by Which? magazine, 15 out of 19 so-called sourdough loaves, sold in supermarkets, that they examined were not made in the traditional way and contain extra ingredients or additives.
Traditional sourdough is considered to be one of the oldest forms of bread and the technique can be traced back to ancient Egypt.
But Which? magazine says it looked at 19 sourdough loaves sold in supermarkets and found only four were made in the traditional way with the three basic ingredients.
The others contained extra ingredients, such as yeast, ascorbic acid and yoghurt and vinegar.
While these are not necessarily bad for you or unhealthy, Chris Young from the Real Bread Campaign says customers are being misled.
"If you are told you are buying something, you should get what you pay for. Particularly when some of the supermarkets are charging a premium for that product," he said.
The Real Bread Campaign group says it wants to see a legal definition of the terms "sourdough" or "artisan bread", so stores cannot "misinterpret" them.