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 UK and Scottish Governments as they prepare to issue their own strategy for tackling obesity in the UK.

The Scottish Government has said it will study the WHO report to "see if there are any lessons" that could inform its policies, but public health minister Maureen Watt said last week that there were "no plans to introduce a sugar tax."

It is understood ministers are to look at the use of multi-buy promotions of high sugar snacks.

The creation of new taxes is broadly reserved to Westminster. Any tax of this type proposed in Scotland would be subject to the approval of the UK Parliament.

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."

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.

Food Standards Scotland (FSS) which was set up 10 months ago to advise the government on food and nutrition, recommended last week that ministers "actively consider how a sugar tax may be introduced and at what rate".

It said that if obesity continues to rise at the current rate 40 per cent of the Scottish population will be obese in 15 years.

Professor Derek Bell, president of the Royal College of Physicians of Edinburgh, said: "Introducing a tax will raise awareness and encourage those selling drinks to be more thoughtful and also encourage manufacturers to review their current production methods and marketing.

"This will only work through a focus on improving diet as a whole as well as encouraging exercise and is a welcome step in the right direction."

Ms Maureen Watt said: “The Scottish Government is continuing to work closely with retailers, including major supermarket chains, to encourage them to offer healthier choices. Part of this work includes encouraging them to shift the balance of their promotions towards healthier options.

“We have no direct power to introduce a sugar, or soda, tax. However, we are examining what further effective actions we can take within the current powers of the Scottish Government that would have an impact on obesity rates, including on the use of multi-buy promotions.

“There are clear health benefits associated with reducing sugar consumption, as part of a healthy diet. We’re taking a range of actions to improve diet, including spending over £10m in the four years to 2016 on projects to encourage healthy eating. These include the Healthy Living Award, the Healthy Living Programme, and Community Food and Health Scotland.

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".