Sustain promotes better food and farming practices. It launched the mark this month to promote bread made to artisan standards, using just flour, water, yeast and salt and no additives and dough fermented for at least four hours.
"I have no objections if it promotes bread made by independent, craft bakers," said Gordon Polson, director of the Federation of Bakers. "But they are trying to suggest there's something implicitly different in my members' bread. All bread is real bread."
Campaign manager Chris Young said the mark was directed at bread sold at all retail levels. "Small, local, independent bakeries is where the demand [for the mark] is coming from. But hopefully supermarkets will see the sales advantages."
Responding to suggestions by Sustain that unwrapped bread sold in supermarket instore bakeries should display ingredients used in it, Polson said: "Obviously according to legislation, wrapped bread has to state all ingredients and unwrapped doesn't, but the real difference is minimal."
Bakers Nicholas & Harris and Doves Farm Foods qualified for the Real Bread Mark, said Sustain, which claimed other bakers had expressed interest in using it on their packaging as well.
Greg Woodhead, new product development manager for bakery company Bakehouse, said it was impractical to insist mass-produced plant bread conformed to the same standards as artisan bread. "The problem is keeping dough hanging around for hours requires a humungous amount of space."
Sustain's mark also failed to recognise the work plant bakers had already done to replace synthetically produced additives with more natural alternatives, he added. "It runs the danger of demonising additives and playing on fears the food industry is putting ingredients into products for its own ends, at the expense of health.
"It does overlook the fact that the food industry is trying to draw a middle line between high quality consumer products made on a mass scale and moving towards more healthy foods. You are not going to be able to do that day in, day out without using additives."
He pointed out that the additive argument was not clear cut. For example, many bakers treat flour with ascorbic acid as a preservative. Otherwise known as vitamin C, it is naturally-derived, so it was unfair to question its use, he said.
Baking aids could be seen as a "mystical" area, he said. But natural aids such as rapeseed oil were often used to help prevent dough from sticking during processing.
The solution to consumer fears was to engage in proper debates about additives, he said.