Starbucks said it is taking action.
"Earlier this year we committed to reduce added sugar in our indulgent drinks by 25 per cent by the end of 2020," a Starbucks spokesperson said. "We also offer a wide variety of lighter options, sugar-free syrups and sugar-free natural sweetener and we display all nutritional information in-store and online."
That promise appears to be not enough for the campaigners.
They says the U.K. needs a new tax on sugar in food and an independent agency that will oversee a reduction in fat and sugar in processed food and drink.
Health experts link excessive sugar intake to health problems such as obesity, tooth decay and type 2 diabetes.
In 2013-2014, diabetes in primary care cost the UK's NHS £2.2 million every day, according to the Health and Social Care Information Centre.
The survey covered 131 hot drinks sold in U.K. retail district outlets.