CASH surveyed 576 different soups available in the UK and found that 48 per cent of the samples contained more than 0.6 grams of salt per 100 grams - the target salt level for soup set by the Food Standards Agency (FSA).
"We congratulate those companies who have managed to reduce the amount of salt in their soups to well below the target," said Professor Graham MacGregor, chairman of CASH and professor of cardiovascular medicine. "But there are a large number of soups (48 per cent of the samples we looked at) that contain more than 0.6g of salt per 100g, and people are inadvertently eating a lot of salt through choosing these soups.
"Some companies have used the 0.6g of salt per 100g level as an absolute target to make sure that all their soups are below this limit, whereas others are using this as an average level. We would rather that all soup manufacturers worked in a responsible way, by not balancing out some very high salt soups with a few low salt products, which will not achieve the objective of reducing salt intake in the whole adult population to less than 6g day," he added.
Salt is a vital nutrient and is necessary for the body to function, but CASH considers the average daily salt consumption in the western world, between 10 and 12g, far too high.
In the UK, Ireland and the USA, over 80 per cent of salt intake comes from processed food, 20 per cent from meat and meat products, and about 35 per cent from cereal and cereal products.
"We are really concerned that the soups mentioned are a major hidden source of salt," said Jo Butten, CASH nutritionist and author of the new report. "This is particularly important as soup generally only forms part of a meal, or, in the case of instant cup soups, is drunk as a snack or as an alternative to tea or coffee during the day."
"We need people to realise that soup can contain lots of salt and we urge them always to choose the lower salt options and avoid all soups that contain more than 0.6g of salt per 100g," she added.
The report looked at a variety of soup formulations from eight retailers, twelve brands and three take-away food chains. These included canned, chilled, packet, pouch, ready-made and instant soups.
CASH report that the soup with the lowest salt content contained only 0.24g salt per 100 grams (Simply Organic), while the highest salt content was found to be 1.0g salt per 100g (Masterfoods' Seeds of Change organic soups and Crosse and Blackwell Soup Cups).
Twenty-two per cent of the soups surveyed contained more than two grams of salt per serving and three per cent contained more than 3g of salt. The average salt content for a serving of soup in the survey was 1.6g.
"Until all manufacturers reduce the salt content of soups, the public needs to be aware and check the label. We would strongly advise people only to choose soups that provide no more than 1.2g of salt per serving," said Professor MacGregor.
Numerous scientists are convinced that high salt intake is responsible for increasing blood pressure (hypertension), a major risk factor for cardiovascular disease (CVD) - a disease that causes almost 50 per cent of deaths in Europe.
CVD is reported to cost the EU economy an estimated €169bn ($202bn) per year.
Yet not everyone agrees with the science behind CASH's claims. Robert Speiser, director of EuSalt, told FoodNavigator last year that he strongly disputes the need for salt intake restrictions.
Speiser's concern is that some regulatory bodies, such as the FSA in the UK, focus on certain scientific studies and neglect others. Indeed, many scientific institutions that hold opinions different to EuSalt, such as the Institute of Food Science and Technology, acknowledge that much is still unknown about the relationship between salt consumption and health.
In addition, salt remains a vitally important compound in food manufacturing in terms of taste and preservation. In processed meat products, for example, salt is involved in activating proteins that increase water-binding activity. It also improves the binding and textural properties of proteins, helps with the formation of stable batters with fat, and extends shelf-life with its anti-microbacterial effects.