Nearly a quarter of all soup bought in supermarkets contains too much salt, with one brand containing more salt than two McDonald’s cheeseburgers, according to research.

Soup has long had a reputation for being a healthy choice for lunch. The analysis of nearly 500 varieties of tinned and chilled soups sold in supermarkets found that 23% contained too much salt.

Of the 481 soups Action on Salt and Sugar (AoSS) tested, nearly half (48%) of branded soups and 6% of supermarket own-brand soups still exceeded the government’s voluntary salt target of 0.59g per 100g serving.

The saltiest was Soup Head’s Tom Yum soup, with 3.03g in a 300g pack – more than half an adult’s recommended total daily limit and saltier than eating two McDonald’s cheeseburgers. Other high-salt soups included Daylesford Organic minestrone soup (1g per 100g) and Baxters luxury Cullen Skink (0.95g per 100g).

Eating too much salt can cause high blood pressure, which increases your risk of a heart attack or stroke. According to the World Health Organization, just under 2 million deaths a year are linked to eating too much salt.

The NHS recommends adults consume no more than 6g of salt, equivalent to one level teaspoon, a day. Adults in England consume on average 8.4g of salt a day, 40% more than this maximum.

AoSS found that nearly 90% of Mr Organic soups, just under 70% of Heinz, 40% of Daylesford Organic and 27% of Crosse & Blackwell soups exceeded the voluntary maximum amount of salt in soup.

AoSS calculated that under front-of-pack labelling guidelines, one in six soups would be classified as red for high salt levels, and only 11 soups would be labelled green.

In contrast, every Tesco, Sainsbury’s, Morrisons, Waitrose, Co-op, Lidl and Covent Garden soup tested had salt levels at or below the government target.

Sonia Pombo, the head of impact and research at AoSS, said the level of noncompliance with targets showed that government action was needed.

“The UK used to be a world leader on salt reduction, but progress has stalled. Government must get back on the front foot with stronger incentives to drive reformulation, and proper accountability, so the healthier option becomes the default, not the exception.”

A Department of Health and Social Care spokesperson said: “This government is bringing in a modernised food nutrient scoring system, which includes criteria for salt, to improve diets, which has a direct benefit to health.

“We are also restricting advertising of junk food on TV and online, limiting volume price promotions on less healthy foods and introducing mandatory reporting on sales of healthy food – all of which should also impact the salt content of foods.”

Dell Stanford, a senior dietitian at the British Heart Foundation, said reducing salt was a quick and cost-effective way to reduce the risk of high blood pressure, but that as most salt consumed was added to foods before purchase, people had “little ability to reduce their intake through individual choice alone”.

A spokesperson for Veetee, which makes Soup Head’s Tom Yum soup, said: “We will continue to assess opportunities to reduce salt and improve nutritional profiles across our range as part of our broader, long-term approach to health and wellbeing.”

A Heinz spokesperson said: “We’ve been reducing the amount of salt in our products since the mid-1980s … Reducing sodium without compromising on taste and quality is a complex process and there’s still work to be done.”

A spokesperson for Mr Organic said: “Over the past five months, we have already been working behind the scenes on recipe development to reduce salt across our soup range … We know there are still very limited options available that focus on lower salt, and we see this as an important opportunity and responsibility for us as a brand.”

Daylesford Organic said: “The salt content figure of 1g per 100g for Daylesford minestrone soup cited in this report was based on a packaging misprint that has been independently verified as incorrect. Laboratory analysis confirms the actual salt content is 0.67g per 100g – 33% lower than reported. Corrected packaging is already in production. We regret this error and are committed to accurate nutritional labelling.”

Andrea Martinez-Inchausti, the assistant director of food at the British Retail Consortium, said: “The retail industry is fully committed to helping improve the health of their customers, with the report showing that retailers are leading the way on product reformulation.

“It is, of course, important to strike a balance between diminishing salt levels while also retaining the quality and taste which consumers expect. The clear labelling on packaging ensures that consumers are fully aware of the salt content in the products they buy.”

A spokesperson for Baxters Food Group said: “We produce many soup products that fall well within the guidelines for salt content. The quality of our ingredients is fundamental to our business and all our soups are free from artificial colourings, flavourings and preservatives.”