The World Health Organisation (WHO) has joined those calling for a "sugar tax" on soft drinks in a major report on childhood obesity.
The move will undoubtedly increase pressure on the Government as it prepares to issue its own strategy for tackling obesity in the UK.
The new report says there is strong evidence that a sugar tax can work alongside other measures, such as tackling big portion sizes and unclear food labelling.
It also calls for a crackdown on the marketing of junk food to children and for schools to ban the sale of unhealthy food.
Calling for a sugar tax, WHO's Commission on Ending Childhood Obesity said: "Overall, the rationale for taxation measures to influence purchasing behaviours is strong and supported by the available evidence.
"The Commission believes there is sufficient rationale to warrant the introduction of an effective tax on sugar-sweetened beverages.
"It is well established that the consumption of sugar-sweetened beverages is associated with an increased risk of obesity."
The report said those on low incomes and their children "have the greatest risk of obesity in many societies and are most influenced by price".
It added: "Fiscal policies may encourage this group of consumers to make healthier choices (provided healthier alternatives are made available) as well as providing an indirect educational and public health signal to the whole population."
Public Health England (PHE) also backs the possibility of a sugar tax of up to 20%.
Prime Minister David Cameron has said he does not see the need for a sugar tax, although his position is believed to have shifted recently.
A PHE report released in November said the levy would tackle the obesity crisis by curbing demand for unhealthy food and drinks.
The study was originally shelved by Health Secretary Jeremy Hunt, but a row between the Government, PHE and MPs on the Commons health committee led to claims it was suppressed.
In its new report, WHO set out a range of measures to tackle childhood obesity, saying: "Processed, energy-dense, nutrient-poor foods and sugar-sweetened beverages, in increasing portion size, at affordable prices have replaced minimally-processed fresh foods and water in many settings at school and family meals.
"The easy access to energy-dense foods and sugar-sweetened beverages and the tacit encouragement to "size-up" through commercial promotions have contributed to the rising caloric intake in many populations."
Members of the Commission said it was no longer sufficient to rely on "simple codes" for food labelling such as the traffic lights system popular in the UK.
They called for tighter regulations around the marketing of food and drinks to children "to reduce the exposure of children and adolescents to, and the power of, the marketing of unhealthy foods".
The report also dismissed efforts by industry, saying: "Despite the increasing number of voluntary efforts by industry, exposure to the marketing of unhealthy foods remains a major issue demanding change that will protect all children equally.
"Any attempt to tackle childhood obesity should, therefore, include a reduction in exposure of children to, and the power of, marketing."
Furthermore, the Commission said parents should be given advice on exercise, healthy body sizes and "appropriate use of screen-based entertainment".
Meanwhile, schools should ban the "provision or sale of unhealthy foods, such as sugar-sweetened beverages and energy-dense, nutrient-poor foods, in the school environment".
The report added: "Childhood obesity is reaching alarming proportions in many countries and poses an urgent and serious challenge.
"Children with obesity are very likely to remain obese as adults and are at risk of chronic illness.
"Progress in tackling childhood obesity has been slow and inconsistent."
Current estimates of UK sugar intake among school-age children are that 14.7% of all calorie intake is made up of sugar.
The main sources of sugar include soft drinks, table sugar, confectionery, fruit juice, biscuits, buns, cakes, pastries and puddings and breakfast cereals.
Soft drinks (excluding fruit juice) are the largest single source of sugar for children aged 11 to 18. They provide 29% of daily sugar intake, on average, for this age group.
A third of 10 to 11-year-olds and over a fifth of four to five-year-olds in England are overweight or obese.