A can of fizzy drink contains more than the recommended daily amount of sugar for children under 11, according to new guidelines from scientific experts.
A report by the Scientific Advisory Committee on Nutrition (SACN) advises the Government to halve the current recommended intake of free sugars in a bid to tackle the growing obesity and diabetes crises, estimated to cost the NHS a combined £15 billion a year.
Free sugars are those that are added to food by manufacturers or those naturally present in honey, syrups and unsweetened fruit juices.
The recommendations - that free sugars account for no more than 5% of daily energy intake - are also hoped to reduce the risk of tooth decay - the number one cause of hospital admissions among children.
The guidelines say the consumption of sugar-sweetened beverages, such as fizzy drinks, soft drinks and squash, should be minimised by both children and adults in particular because of their links to weight gain and the increased risk of developing type 2 diabetes.
The Government said it is accepting the recommendations and will be using them to develop its forthcoming national strategy on childhood obesity, due out later this year.
But it has said it will not be introducing a sugar tax, which has been suggested by many, with doctors' union the British Medical Association (BMA) becoming the latest to join the call this week.
Health campaigners have also accused the Government of pushing back a review by Public Health England (PHE) on how these measures could be implemented by the public.
A spokesman denied claims that it had been pushed back, but campaigners said the time difference between the two reports will mean a vital opportunity to show how to introduce a healthier diet is lost.
Health experts said 5% of daily energy intake is the equivalent of 19g or five sugar cubes for children aged four to six, 24g or six sugar cubes for children aged seven to 10, or seven sugar cubes for those aged 11 and over, based on average population diets.
They said an average can of fizzy drink contains about seven sugar cubes, while there are around eight in the average bowl of ice cream.
The report from SACN - an independent body of expert nutritionists which advises Government on matters relating to diet, nutrition and health - also advised that children and adults should increase the amount of fibre in their diet by eating more fruit, vegetables and wholegrain foods.
It said those aged 16 and over should raise their intake of fibre to 30g a day, or 25g for 11 to 15-year-olds, 20g for those aged five to 11, and 15g for two to fives.
The report maintains the current recommendation that starchy carbohydrates - particularly wholegrain - should form 50% of daily calorie intake.
Professor Ian Macdonald, chairman of the SACN Carbohydrates and Health working group, said: "The evidence is stark - too much sugar is harmful to health and we all need to cut back.
"The clear and consistent link between a high-sugar diet and conditions like obesity and type 2 diabetes is the wake-up call we need to rethink our diet.
"Cut down on sugars, increase fibre and we'll all have a better chance of living longer, healthier lives."
The report, which was published in draft form in June last year, echoes advice by the World Health Organisation (WHO), which also recently recommended reducing added sugar from 10% to 5% of energy intake.
The British Dental Association (BDA) said that, with 46,500 people under 19 admitted to hospital with tooth decay in a single year, it has long championed action on sugar.
Its chairman, Mick Armstrong, said: "We have an historic opportunity here to end Britain's addiction to sugar.
"The Government now has the evidence and a clear duty to send the strongest possible signal to the food industry, that while added sugar might be helping their sales, it is hurting their customers.
"Tooth decay remains the number one reason for hospital admissions among young children. By halving recommended sugar intake we could start bringing down the multimillion-pound bill we all pay for expanding waistlines and sick mouths."
British Dietetic Association chairwoman Dr Fiona McCullough said: "The time is now right to address this issue head on and improve the nation's health in both the long and short term.
"Let's make no mistake that the recommendations sitting on the desk of the Government will be challenging to deliver, but I can assure you that dietitians around the UK are up for this challenge.
"The experts have presented credible evidence and the ball is now firmly in the Government's court to seize this opportunity to improve the nation's health. While we all have a personal role to play in our individual health and the health of our families, we do need political will and momentum behind this."
Public Health Minister Jane Ellison said: "This report confirms that, as a nation, we eat and drink too much sugar, which has a direct impact on our health.
"We are accepting the recommendations made in this expert report and the Government will be using them to develop our forthcoming national strategy on childhood obesity."
The Food and Drink Federation described the goals set out in the report as "stretching".
Director general Ian Wright said: "The most thorough scientific review of carbohydrates and health carried out in recent years should leave people in no doubt that sugars can be enjoyed safely as part of a varied and balanced diet.
"Sensationalist commentaries on this everyday ingredient that are not based in science should now be relegated to the past.
"Demonising any one ingredient in the obesity debate isn't helpful."
He went on: "To meet the stretching dietary goals that SACN recommends will mean changes to the way people eat.
"Published diet modelling shows that people can reduce free sugars and boost fibre in the diet in a number of ways while still fitting in the foods and drink they enjoy.
"We hope SACN's key recommendations will be translated into meaningful and practical diet and lifestyle messages which are consistently used by everyone with a voice in the health debate."
And he added: "UK food and drink businesses remain committed to helping our customers achieve better, more balanced diets. We will continue to engage with Government and other partners and to be part of the solution to tackling obesity."