The cafes serving drinks with 25 teaspoons of sugar per cup
Millions of Britons are putting their health at risk by ordering hot chocolate and other trendy chai drinks that contain staggering amounts of sugar - up to 25 teaspoons - in just one serving, Kazinform reports.
Action on Sugar found that 98% of the 131 hot flavoured drinks found in the big high street chains would carry a "red" warning for excessive levels of sugar if the coffee shops were forced to label them, The Guardian reports.
The campaign group named Starbucks's Hot Mulled Fruit (grape with chai, orange and cinnamon venti) as the worst offender. At 25 teaspoons of sugar it contains more than three times the recommended maximum adult daily intake.
Costa's largest chai latte was found to contain 20 teaspoons of sugar, while an extra large Signature hot chocolate from Starbucks contained 15 teaspoons, double the daily adult maximum.
More than one-third of the drinks tested were found to contain the same - or higher - levels of sugar as a can of Coca-Cola.
The high street chains have increasingly offered chai, chocolate and other hot drinks to attract non-coffee drinkers. They also offer high-sugar syrups to add extra flavour.
It is thought up to 20% of the population visit a coffee shop on a daily basis, but many will be unaware how much hidden sugar they are consuming in flavoured drinks.
Action on Sugar has called on the coffee chains to stop serving extra-large cups of sugar-laden hot drinks. It singled out Starbucks for criticism because, it said, its serving sizes were much larger than those offered by its competitors.
Starbucks told the Guardian it was committed to reducing added sugar in its indulgent drinks by 25% by the end of 2020, and that "all nutritional information is available in-store and online".
Costa said it had already taken significant steps to reduce the sugar content of its ranges, and that in April it would be setting salt and sugar reduction targets for 2020.
Kawther Hashem, registered nutritionist and researcher for Action on Sugar, said these hot flavoured drinks had to become an occasional treat, rather than an everyday purchase.
"They are laden with an unbelievable amount of sugar and calories and are often accompanied by a high sugar and fat snack. It is not surprising that we have the highest rate of obesity in Europe.
"Our advice to consumers is to have a plain hot drink or ask for your drink to contain a minimal amount of syrup, preferably sugar-free, in the smallest serving size available."
Graham MacGregor, professor of cardiovascular medicine at Queen Mary University of London, described the findings as further evidence of the "scandalous amount of sugar added to our food and drink".
He called on the prime minister, David Cameron, to urgently establish an independent agency for nutrition that is "not controlled" by the food industry.
In 2012 the food industry agreed a series of voluntary pledges with the Department of Health in which it committed to ensure that Britons consumed 5bn less calories a day. However, the "responsibility deal", as it is termed, has been criticised as failing to deliver any real impact.
Action on Sugar has called for a 50% reduction in sugar and a 20% reduction in fat in all unhealthy drinks and foods within five years, and a ban on all forms of advertising of unhealthy foods and drinks to children and adolescents.
In November a hard-hitting report from MPs said a 20% sugar levy was an essential part of any national strategy to tackle child obesity.