Some supermarket yoghurts may contain more sugar than Coca Cola despite being regarded as “healthy”, a new study has warned.

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.

A typical yoghurt contained more than half an adult’s daily recommended sugar allowance. The researchers assessed the nutrient content of almost 900 yoghurts and yoghurt products, which were available from five major UK online supermarket chains in in late 2016.

Under the traffic lights nutritional labeling system, products with less than than 5g of sugar per 100g can be given the green rating, while those with 22.5g per 100g are considered high in sugar.

However, only those labelled “natural” or “Greek” qualified as low-sugar products.

The total average sugars included in organic yoghurt was 13.1g per 100g and in children’s yoghurts it was 10.8.

There is 10.6g of sugar per 100ml of Coca Cola. A millilitre of water weighs the same as a gram. The recommended daily allowance of sugar is 30g.

Only two per cent of children’s yoghurts were classed as low in sugar.