This is especially true of the yogurts in the organic category, which are generally regarded as a healthier alternative.
The levels were significantly higher even in "organic" style yogurts while baby and kids yogurts were also high in sugar.
Scientists from the Universities of Leeds and Surrey analysed the product information for 921 yogurts available in major United Kingdom supermarkets.
They therefore assessed the nutrient content of nearly 900 yogurts and yogurt products, which were available from five major United Kingdom online supermarket chains in October/November 2016.
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.
In these categories, total average sugars ranged from 10.8g/100g in children's products to 13.1g/100g in organic products. "I did not know that the yogurt I was giving my child had [so much] added sugar in it", Moore said in a statement to ABC News.
"Our study highlights the challenges and mixed messages that come from the marketing and packaging of yogurt products", she said.
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Less sugar in Greek and natural yogurt: 100 grams of the product found 5 grams of sugar.
Doctors say that the normal amount of sugar for a child for one day - 19 g.
Researchers have found that fewer than one in ten categories of yoghurt sold in British supermarkets qualify as low-sugar, with brands labelled "organic" or those marketed at young children among the most sugary.
Although yoghurt has always been considered a healthy food, experts warn that numerous products sold in supermarkets could contribute to child obesity, tooth decay and other health problems due to their high sugar content.
'An alarming 58% of women and 68% of men - along with one in three of United Kingdom children aged ten to eleven - were overweight or obese in 2015. The Government is targeting yogurt as part of its childhood obesity plan, and wants companies to remove 20 per cent of sugar by 2020.
"It can be a great source of protein, calcium, and vitamin B12".
A new study found that yogurts have deceptively high levels of sugar, with organic yogurts being some of the worst. "Many portion sizes for children's yogurts were identical to adult portion sizes". But, with the exception of natural/Greek yogurts, the average sugar content of products in all the categories was well above the low sugar threshold.
According to the study, only natural and Greek yogurts fell below the advised 5g of sugar per 100g recommended by European Union regulations, while the study found that organic varieties, often viewed as healthier options on average contain around 13.1g of sugar per 100g.