Keeping track of how many calories and fat in our lunch would be easier if popular high-street sandwich brands clearly labelled the nutritional value, consumer watchdog Which? has warned.

The report claims confusing and contradicting labels on lunchtime favourites are making it hard for consumers to make correct comparisons when choosing the healthier option.

Tesco, Aldi, Greggs, Morrisons and Caffe Nero were all criticised for their lack of ‘traffic light labelling’ on pre-packed sandwiches.

The standard labels, created by the Foods Standards Agency, should include a colour-coded wheel indicating the salt, saturated fat and calorie content – with red, amber and green measuring how high or low the nutrient levels.

Food retailers who do use the traffic light labelling system include Asda, M&S, Sainsbury’s and Boots.

As portion size and nutritional content vary from sandwich to sandwich, Which? point out consumers could be eating three times as much fat and double the amount of salt in apparently 'equivalent' meals.

Shocked? Take a look at other hidden fat traps lurking in your everyday food…

To illustrate their concerns, Which? focused on three popular sandwiches – chicken salad, egg mayonnaise and bacon, lettuce and tomato (BLT).

They discovered a chicken sarnie from Morrisons contained 11.7g fat compared to one from Waitrose which contains 6.0g fat. A BLT from Lidl racks up 3.36g of salt, whereas in Boots, the same sandwich contains 1.5g salt.

Incidentally, the sandwiches with the highest levels of fat and salt were the ones without the traffic light labelling.

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"With obesity levels reaching epidemic proportions, it's more important than ever that consumers know exactly what they're eating,” Richard Lloyd from Which? said in a statement.

“Many retailers are already using traffic-light labelling, but the rest need to catch up and do what works best for consumers. We want to see the government insist that all food companies use traffic lights on their labels, so there's a clear, consistent system that makes it easier for people to make informed choices about what they eat."

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• Tuna And Sweetcorn

  Individuals that pick tuna and sweetcorn on white bread love order, routine and targets. They can often find it hard to relax, work ahead of deadlines, can be high achievers and have a tendency to believe they are always right. They enjoy a range of hobbies and seek friends who share the same drive and beliefs as them.

• BLT On Seeded Bread

  The BLT on seeded bread eater lives in the now, believing that experience speaks louder than words. Those that pick this sandwich are often self-indulgent and materialistic. They love eating out, films and live music. A good sense of humour in friends and partners is a must.

• Cheese And Pickle

  Those who go for the classic cheese and pickle are logical planners who like to surround themselves with successful people. They tend to be good at tasks and will always tell the truth no matter how tactless it may seem. They love solving things and are a fan of games and puzzles.

• Prawn On Brown Bread

  Those who pick a prawn sandwich on brown bread are friendly and tactful in any situation. They are sensitive and tend to be very unsettled by conflict. The need to agree with others can make them easily led. They love fashion and shopping and seek friends with a good sense of humour.

• Beef Roll

  The beef roll lover acts first and then thinks later. They love to solve problems and are great at multi-tasking. They often have an unwillingness to commit to anything that will interfere with their freedom. In a partner they seek someone who is attractive and they enjoy the thrill of spectator sports.

• Ham On White Bread

  The ham salad on white bread lover often spends time thinking about their future. They are inventive and original. A real love of physical activity and the outdoors, they gain inspiration from their surroundings at the expense of observing and experiencing them.

• Chicken Wrap

  Those who pick a chicken salad wrap are sociable and talkative and thrive on interaction with the outside world. They do tend to act without thinking things through. They enjoy spending time watching sports and seek a partner with a strong career success.

• Egg Mayonaise

  Those who prefer an egg mayo on wholemeal are reflective, quiet people, they like to spend time alone and are motivated by private, internal goals. They find social situations draining and instead prefer to spend time at home. In a partner they seek someone with similar interests and values to themselves.