Imposing a 10% "fat tax" on sugary drinks would help tackle soaring rates of obesity, according to new research by international experts.

A price hike would cut consumption of heavily sugared drinks, which have been blamed for expanding waistlines, and prompt consumers to switch to healthier alternatives, claims the study, which has been published in the British Journal of Nutrition (BJN). Its four co-authors include Professor Susan Jebb, an eminent nutrition specialist who has been the government's main adviser on obesity since 2007.

A growing number of countries worldwide are considering extra taxes in order to drive down sales of "unhealthy" products which contain a lot of saturated fat or sugar. David Cameron said in October that the coalition would consider following the example set by Denmark, which days earlier introduced a "fat tax" on foods containing more than 2.3% saturated fat as a way of minimising the huge and rising medical harm and financial cost to its health service caused by obesity.

Britain's hospital doctors on Wednesday said such measures could be effective in reducing obesity. "The Royal College of Physicians supports legislative measures to tackle major public health issues, such as obesity, where there is substantial evidence to support it," said Professor John Wass, chair of the college's obesity working party.

"Legislative measures have already worked in France, where food and drink in schools is controlled and all marketing of foods high in fat, sugar and salt is banned unless they are taxed and marketed with a health warning. Studies have shown that following these measures, the number of overweight children in France has dropped from 18.1% in 2000 to 15.5% in 2007," he said. The RCP is "sceptical" that health secretary Andrew Lansley's emphasis on "nudging" consumers to adopt healthier lifestyles will succeed and believes that "the additional force of legislation or financial pressures" is necessary, Wass added.

The BJN study analyses trends in consumption of all drinks by both children and adults in Britain between 1986 and 2009. It also estimates the likely impact of a 10% increase in the price of sugar-sweetened beverages (SSBs). "In testing taxation as an option for shifting beverage purchase patterns, we calculate that a 10% increase in the price of SSBs could potentially result in a decrease of 7.5ml per capita per day." A similar 10% hike in the cost of full-fat milk would also reduce consumption of it by 5ml per person per day and increased intake of reduced fat milk by 7ml per head every day, it adds.

"This analysis implies that taxation or other methods of shifting relative costs of these beverages could be a way to improve beverage choice in Great Britain," it adds. As well as Denmark's tax on saturated fat, the French parliament is planning to introduce a soft drinks tax, Hungary has already brought in an extra levy on all "high-fat-sugar-salt" products, while Finland is doing the same with sweets. Many American cities are also debating whether to tax soft drinks, though Ireland brought one in but then abandoned it.

Dr Mike Rayner, an obesity expert and public health researcher at Oxford University, said: "This research adds to the increasing weight of expert opinion that fiscal measures are an underused mechanism which may prove to be an important public health tool for influencing people's food choices away from those high in saturated fat, salt or sugar." Ministers should now commission "an independent review which would make recommendations on UK taxation on unhealthy foods, considering both economic factors and health outcomes", Rayner added.

But Jack Winkler, a professor of nutrition policy, said the 10% soft drinks tax would be "ineffective". In a response in the BJN to the plan he said that the idea, while well-intentioned, would make no difference to obesity. Consumers would simply buy larger bottles, use cheaper shops, drink cheaper brands or buy soft drinks on "special offer", he warned. As many consumers are prepared to pay 950% more for Coca-Cola than cheap, unbranded cola, few people would be deterred by a 10% price rise, he said. Soft drinks manufacturers should instead cut the price of their sugar-free drinks, which contain sweeteners instead of sugar, as their contribution to greater public health, Winkler said.

The soft drinks industry branded the idea "ineffective, intrusive and unfair". Richard Laming, media director of the British Soft Drinks Association, said: "A tax on soft drinks is not the way to fight obesity. The cause of obesity is an excess of calories in the diet over calories expended in exercise, and not the overall amount of calories consumed, still less the calories from any individual source. Many people enjoy soft drinks within a balanced diet: those people should not be targeted for additional taxes. Balanced diets and active lifestyles can only be achieved through information and education and not regulation or compulsion."

The study itself states that while overweight and obesity have risen in recent years, "energy from beverages has not shifted markedly overall during the past decade in Britain", added Laming.

The Department of Health refused to say if it supported a soft drinks or any other "fat" tax. A spokeswoman said: "This research is one of a number of independent academic papers that looks at the likely impact of taxes on food products. It does not call for a 10% tax on sugary drinks. We keep all international evidence under review."

She added: "We are taking action to reduce energy intake through a calorie reduction challenge to the nation, launched as part of our Call to Action on Obesity, and are talking to business and others about the actions that can be taken in response." The department was criticised last month for disbanding its expert advisory group after some members criticised Lansley's focus on "responsibility deals" with the food industry and backed tougher measures, including the use of "fat taxes". Jebb chaired that group, but has been retained as the DH's science adviser on obesity – her role since 2008 – and co-chair, with Lansley, of the responsibility deal's food network. Downing Street did not respond to a request to comment.