Of 921 yoghurts available in United Kingdom supermarkets in October and November 2016, organic ones had an average sugar content of about 13.1g per 100g, the highest content excluding those sold specifically as desserts.
Researchers at Leeds University in the United Kingdom, headed by nutritionist Doctor Bernadette Moore, who published the research in the British medical journal, analysed 921 yogurts available in large British supermarkets.
Only two of the 101 children's yogurts and fromage frais surveyed could be classified as low sugar, with most having 10.8g per 100g.
High sugar levels in yogurt are particularly problematic due to their reputation as a healthy food. Although yogurt, cereals, and candies did manage to reduce overall sugar levels by 5%.
The researchers note that yoghurt is an important source of nutrients including calcium, protein and vitamin B12, and is linked to digestive benefits.
In these categories, total average sugars ranged from 10.8g/100g in children's products to 13.1g/100g in organic products.
The NHS recommends that children aged four to six have no more than 19g of sugar, or five sugar cubes a day, and it is advised that those aged seven to 10 consume less than 24g daily. The Government is targeting yogurt as part of its childhood obesity plan, and wants companies to remove 20 per cent of sugar by 2020.
Apart from products in the dessert category, organic yogurts were found to have the highest average sugar content - roughly 13.1 grams per 100 grams.
Organic varieties were the worst offenders, typically containing 13grams of sugar per 100g.
Study co-author Annabelle Horti, who conducted this research while at the Leeds" School of Food and Nutrition, said: "Changing the public desire for "sweeter' yogurts may be a real challenge when it comes to reducing its sugar content". This may be why these products had higher amounts of added sugar to offset the sourness.
"Sugar is often used as a sweetener to counteract the natural sourness from the lactic acid produced by live cultures in yogurt".
All the products were grouped into eight categories: children's, which included fromage frais; dairy alternatives, such as soy; desserts; drinks; flavoured; fruit; natural/Greek; and organic.
Moore noted that the values only reflect the total sugar content, as labels do not separate naturally occurring sugars such as lactose from added sugars, but said the research suggests approximately 5g of sugar per 100g can be thought of as largely being lactose, with levels above that coming from added sugar.