Essential Waitrose Pure Pineapple Juice contains six teaspoons, as does Capri-Sun blackcurrant juice drink.

Although fruit juice contains natural sugars like fruit, in processing the sugars in the cell walls are released as ‘free sugars’ which damage teeth further and provide unnecessary calories.

And a quarter of drinks surveyed even contained added sugar or glucose-fructose syrup. The ‘no-added sugar’ version of ASDA’s Chosen by Kids Tropical Juice Drinks contained less than one spoonful, giving some indication of how much is added to the

Health experts from Action on Sugar warned parents to avoid fruit juices altogether unless it was at mealtimes. They also advised watering down drinks or swapping them for plain water.

“Our advice is to eat the fruit, don’t drink the juice. Juice should be an occasional treat, not an ‘everyday’ drink,” said Katharine Jenner, Campaign Director of Action on Sugar.

“These processed drinks are laden with sugar and calories and do not have the nutritional benefits of fresh fruit and vegetables.”

The World Health Organisation currently advises that people get a maximum of 10 per cent of total energy from added sugars – around 50g or 10 teaspoons. However a recent study by University College London suggested that figure should be slashed to 14g, or just three teaspoons, meaning the daily limit would be reached from just half a can of Coke.

Too much sugar doesn’t just lead to tooth decay. It can also cause obesity and Type 2 diabetes.

One in five children aged between four and five are already clinically overweight or obese and one in three between the ages of 10 and 11.

“It is not just tooth decay but there is increasing scientific evidence that regular sugary drink consumption is associated with an increased risk of type 2 diabetes and heart disease, independent of body weight, suggesting we are all vulnerable,” said Dr Aseem Malhotra, Cardiologist, Action on Sugar.

“Fruit juice and smoothies should not be part of a healthy balanced diet.”

The report authors found that drinks did not need to be so sweet. Innocent 100% Apple Juice for Kids contains 15.6g of sugars per 200ml, a third (32%) less than Morrison’s Apple Juice From Concentrate which has 22.8g of sugars per 200ml.

Campaigners looked at 2O3 products and found over one-in-four (57) had the same amount or more than Coke. If they used a traffic light system, 117 would have the red warning.

And many are targeted at adults who think they are buying healthy options for their children.

“It is a complete scandal that these drinks are marketed to children and parents as if they are ‘healthy’: this has to stop,” said Professor Graham MacGregor of the Wolfson Institute, Queen Mary University of London.

“We need to stop Britain’s childhood obesity epidemic spiralling out of control.”

Current UK guidelines state a small (15Oml) glass of unsweetened 1OO per cent fruit juice can count as one of your ‘5 a Day’. But Action on Sugar said this recommendation should be withdrawn. And only six products are actually sold in 150ml portion size packaging, making it harder for parents to make a healthy choice for their children.

Nutritionist Kawther Hashem said: “It is highly concerning that many parents are still buying fruit juices and juice drinks for their children thinking they are choosing healthy products; children should be given as little juice as possible.

“What is more concerning are the products with added sugar and glucose-fructose syrup. We call on all manufacturers to stop adding more sugars to already sweet juices, particularly in children’s products.”

A spokesman for Tesco said: “We have cut the number of calories in our soft drink ranges by over three billion and we will be the first major retailer to remove sweets and chocolate from checkouts across all stores.

“We’ll continue to take action like this because we know it’s what our customers want us to do.”

A spokesman for Sainsbury’s added: “We are unhappy with these comparisons as our smoothies come in 90ml pouches and the data refer to a 200ml portion. Juices and smoothies are naturally sweet and we’ve done a lot of work to make our labelling clear and to reduce sugar levels in our ranges.”

Asda said:“Our customers wouldn’t be surprised to learn that fruit juice contains natural sugars. Our product is naturally sweet and has no added sugar.”

Fiona Hunter, independent nutritionist and member of the British Dietetic Association said: “Most nutritionists and dietitians agree that juice can be part of a varied, healthy diet for the whole family. In fact the Government’s healthy eating advice, the Eatwell Plate, includes juice as part of a balanced diet.

“100 per cent pure fruit juice is nutrient rich, so whilst it contains only natural sugar from the fruit, it also adds real nutritional value to the diet with vitamins and minerals including vitamin C, potassium and folate.”