An investigation by Which? magazine has highlighted the need for clearer front-of-pack nutrition labelling including ‘traffic light’ colour-coding, which not every retailer supports.

The research reveals that some sandwiches contain three-times as much fat and double the amount of salt as the same sandwich bought elsewhere, with only six out of the 15 retailers compared by Which? currently using the traffic light system.

Richard Lloyd, executive director at Which?, said: “With obesity levels reaching epidemic proportions, it’s more important then ever that consumers know exactly what they are eating.”

Highlighting discrepancies, researchers also found that fat and salt content varied widely and inconsistent labelling across stores meant that healthier sandwich options were not always obvious.

Examples included Morrisons’ chicken salad sandwich containing 11.7g fat (amber/medium), compared with a similar product from Waitrose, which contained 6g fat (green/low) and uses the traffic light system on its packaging.

Boots, which also uses the same colour-coded nutritional labelling system, has 1.5g salt (amber/medium) in its BLT sandwich, compared to Lidl’s version containing 3.36g salt at a red/high level.

Lloyd added: “We want to see the government insist that all food companies use traffic lights on their labels, so there is a clear consistent system.”