The report, published by the UK-based Consumer's Association in last week's issue of Which?, offers further evidence that the British public may not be getting adequate vitamin intake through their daily diets.
It notes that supermarkets dominate British fruit and vegetable supply but that they often place more emphasis on looks than taste.
Nutrition is not a priority for many supermarkets, it claims, pointing to research that found vitamin C levels in some pre-sliced and packaged supermarket fruit and vegetables were far below normal levels for unprepared produce.
Asda sliced runner beans, for example, contained just 11 per cent of the textbook level of vitamin C, and Marks & Spencer's fresh mango contained just 42 per cent.
The UK's food authority says that adults need 40mg of vitamin C daily although some research suggests that higher amounts can offer important protection against disease such as cancers.
But vitamin levels in fresh fruit decrease after they are picked, and particularly after they have been cut and exposed to air or sunlight. Much of the peeling and chopping of ready-prepared produce is now done abroad and the food then undergoes a long journey.
Malcolm Coles, editor of Which?, said: "Supermarkets should give shoppers more information about where their food comes from, how it's been prepared and how nutritious it is."