Pret A Manger has revealed it is to trial sliced sandwich bread free from all additives except ascorbic acid following claims by The Real Bread Campaign that the chain is serving baked goods containing additives to “unsuspecting customers”.

Campaigners said that - despite stating on its Facebook page that “We avoid the obscure chemicals, additives and preservatives common to so much ‘prepared’ and ‘fast’ food” - Pret uses additives in some of its baked products.

The Real Bread Campaign, which encourages businesses to sell additive-free loaves, also claimed Pret does not make consumers aware of the additives in its sandwiches.

“We urge Pret A Manger to come clean, first by displaying lists of all ingredients, including additives, on packaging or at point of sale and bringing its marketing messages in line with its practices,” said Real Bread Campaign coordinator Chris Young. “No artificial additive is necessary to make bread and ultimately we would like to see Pret, and all other sandwich sellers, removing all artificial additives.”

In response to The Real Bread Campaign claims, Pret A Manger CEO Clive Schlee said his company strives to avoid the use of artificial additives.

“Whilst all our bloomer bread, brioche, flatbreads and stone-baked baguettes are made without any artificial additives at all, sliced sandwich bread is trickier as it can fall apart easily,” he added. “We therefore need to use small amounts of widely-used emulsifiers in order to achieve dependable quality for the volume of sandwiches we make.”

Schlee said Pret had been working to create a loaf that will make a “good-quality” sandwich without the use of additives, and has developed a new recipe free from all additives apart from ascorbic acid (a form of vitamin C), which he said plays “an essential role in strengthening the dough”.

The new recipe will be tested in Pret stores from next year, he added.