Action on Sugar said those looking for an alternative to cow’s milk are unknowingly consuming excessive sugar due to a lack of labelling and the perception that vegan options are healthier.
The charity, based at Queen Mary University of London, analysed both the sugar and calorie content of the largest available sizes of 124 hot chocolates and 79 seasonal lattes made with milk and milk alternatives.
It found that certain seasonal beverages contain almost as much sugar as three cans of Coca-Cola, with almost all of the largest available size products receiving a red traffic light for total sugars.
Action on Sugar said 27% of products directly comparable with a similar study in 2016 had increased their sugar content.
A regular vanilla latte from KFC had 19g of sugar in 2016 but now contains 26g, though a mocha from the outlet has reduced from 45.1g of sugar to 21g over the same period.
Costa has decreased the sugar content of some products by more than 50% since 2016.
Registered nutritionist Holly Gabriel, of Action on Sugar, said: “It is shocking that so many high street coffee chains are wilfully putting their customers’ health at risk despite Public Health England (PHE) setting sugar reduction targets for sugary milk drinks in 2018.
“Responsible coffee shops have shown reformulation is possible within this category.
“For example, Costa have made some significant reductions in sugar since 2016 and some now offer smaller sizes as standard for seasonal drinks.
“Coffee shops and cafes need to take much greater steps to reduce the levels of sugar and portion sizes, promote lower sugar alternatives and stop pushing indulgent extras at the till.”
The study found that Starbucks’ Signature Caramel Hot Chocolate with whipped cream, using oat milk and in venti size, had the highest sugar content of the hot chocolates surveyed.
It contained more than 23 teaspoons, or 93.7g, of sugar and 758 calories – equivalent to four white chocolate and strawberry muffins from Tesco.
The seasonal latte with the most sugar is the Starbucks Gingerbread Latte with oat milk in venti size, containing more than 14 teaspoons of sugar and 523 calories.
There were variations in the sugar content of milk alternatives used in hot chocolates and seasonal lattes.
A venti latte with oat milk from Starbucks had more than seven teaspoons of sugar and 350 calories.
But a venti latte with almond milk from Starbucks contained under three teaspoons of sugar and 121 calories.
Katharine Jenner, campaign director at Action on Sugar, said: “You can always add sugar in, but you can’t take it out.
“Customers looking for dairy alternatives could be shocked to learn that many coffee shops and cafes use pre-sweetened alternative milks as the nutrition information is often very difficult to find – with information only available on websites or not at all.”
She called for coffee shops to display clear nutritional information at the point of sale.
In the study, hot chocolates and seasonal lattes were surveyed across Caffe Nero, Starbucks, Costa, KFC, Greggs, McDonalds, EAT, Leon and Pret.
Seasonal lattes were classed as any drink offered as a seasonal special and including the term latte in the product name.
Researchers used nutritional information found on company websites between November 11 and 22.
Professor Graham MacGregor, chairman of Action on Sugar, said it is “vital” that the next government fully commits to the target of halving childhood obesity by 2030.
“This will mean giving full control to PHE to deliver a robust prevention programme and the authority to ensure that a largely irresponsible food industry fully complies – and that must include taxing these sugary milk-based drinks in the same way as soft drinks,” Prof MacGregor said.
Dr Saul Konviser, of the Dental Wellness Trust charity, described the findings as “deeply concerning” as many children also consume sugary festive drinks.
“Every day, at least 100 children are in UK hospitals having rotten teeth pulled out because of decay caused by sugary food and drinks that is entirely preventable,” Dr Konviser said.
“It is high time coffee shops and cafes act more responsibly and that means reducing the sugar and portion sizes across their drinks menu and stop putting profits before the health of our nation which is feeding the UK’s obesity, Type 2 diabetes and tooth decay crisis.”
A spokesman for Starbucks said: “We would like to highlight that all Starbucks drinks can be customised, such as asking for our smallest size – short; requesting skimmed milk; and less or no whipped cream.
“To help make it easier for customers to make informed choices, nutritional information is also available in-store, on our mobile app and online.
“We are committed to reducing sugar in all our beverages and, since 2015, we’ve delivered a 9% reduction in the sugar content of our gingerbread and core syrup range of vanilla, caramel and hazelnut.”