Coca-Cola is promoting a controversial health awareness campaign after calls for a tax on sugary drinks.

The company has launched television adverts featuring clear information about the calorie content of its drinks and raising awareness of lower calorie alternatives.

The soft drinks giant is also encouraging people to be active and take part in regular exercise as part of its pledge to help fight obesity.

However, as Coca-Cola Great Britain revealed its plans, nutrition experts warned the campaign was likely to be nothing more than a PR exercise.

Dr Jennie Jackson, of Glasgow Caledonian University's Human Nutrition and Dietetics department, said: "I suspect this is a marketing strategy in response to concerns about a sugary drink tax.

"Although I have no doubt its programmes to promote sport in disadvantaged communities are doing good work, I'm uncomfortable that children may subconsciously associate the maker of obesogenic sugary drinks with healthy living."

Mike Lean, chairman of Human Nutrition at Glasgow University, added: "If Coca-Cola was serious about making a difference it would take the caffeine out and reduce the sweetness of its drinks, not just nudge the proportion of sugary drinks sold. That will achieve nothing."

The obesity problem linked to sugary drinks is particularly acute north of the Border, where the most recent Scottish Health Survey claimed more than one in four people aged between 16 and 64 was grossly overweight.

The survey, produced for the Scottish Government, warned obesity rates could reach 40% by 2030. Figures also suggest that 31% of Scottish children aged seven to 11 are overweight.

Last month, the Academy of Medical Royal Colleges (AoMRC) – which represents nearly every doctor in the UK – called for fizzy drinks to be heavily taxed in a bid to tackle the problem.

It also urged the UK Government to ban pre-watershed TV advertising.

A report by food and farming charity Sustain also revealed more than 60 other organisations were backing the calls, including the Royal College of Physicians in Edinburgh and the Scottish Cancer Prevention Network.

The Coca-Cola adverts appeared on ITV and Channel 4 last night. The first, Coming Together, reminded viewers all calories count in weight management, including those in Coca-Cola's products and brands.

The second, Be OK, gave clear information on the calories in a can of Coca-Cola and how much physical activity a consumer needs to do to burn them up. It also promoted the lower calorie alternative, Coca-Cola Zero.

The company is also launching a print media advertising campaign.

James Quincey, president of Europe Group, The Coca-Cola Company, said: "Obesity is a serious problem and I am determined we will take more actions to help address it."

The manufacturer claimed it was also taking further action to implement the commitments it made 11 months ago on signing the Department of Health's Responsibility Deal Calorie Reduction Pledge. This includes introducing a new version of Sprite with 30% fewer calories and launching new advertising for Coca-Cola Zero.

l Experts at Aberdeen University say obesity rates are generally falling, except in deprived communities. They analysed data for children aged between five and six going back 36 years and compared the body mass index of 195,000 youngsters.