Malcolm Clark is not in the habit of confusing children. But on a foggy Saturday morning at the foot of the London Eye, as the queue for tickets gets longer and longer, he does just that. Clark approaches each family braced against the cold and offers them a brand new toothbrush. The kids pull on their parents’ coat sleeves, part intrigued and part worried.

“Here’s a toothbrush to mark the start of the London Eye sponsorship by a sugary drinks company,” he tells them. By 3pm, he has lost his voice.

After closing for its annual maintenance period in early January, the London Eye, one of the most recognisable landmarks in the world, reopened this weekend as the Coca-Cola London Eye. The new name is a result of a sponsorship deal that was signed last September. It means that each pod of the Eye now has Coca-Cola branding inside, that staff wear red tops with Coca-Cola stamped on the back, security staff wear Coca-Cola beanie hats, all the cafes in the ticket office are branded with large Coca-Cola posters, and the wheel no longer shines blue at night, but a vivid, Coca-Cola red.

The move has concerned medical professionals and children’s charities, who believe that such blatant branding will have implications on public health. As co-ordinator of the Children’s Food Campaign, Clark and his team of volunteers handed out 500 toothbrushes on Saturday – the same as the number of children aged five to nine hospitalised every week due to tooth decay. “It’s totally inappropriate for a major family attraction to be sponsored by a sugary drinks company,” Clark said. “It sends completely the wrong message, not just to children and their parents here in London, but – given the Eye’s worldwide recognition and visitor profile – right across the globe.

“Soft drinks are the largest single source of sugar in children and teenagers’ diets, and their regular consumption is associated with weight gain and obesity, diabetes, heart disease and poor dental health. Coca-Cola has been talking about Coke Zero, Diet Coke, and Coke Life, but this branding is completely red for full-sugar Coca-Cola.”

Clark’s charity has been calling for a ban on junk food advertising before 9pm and for Britain to follow France, Mexico and Hungary in introducing a 20p per litre tax on sugary drinks. Supporters say this tax, backed by more than 60 organisations including the Academy of Medical Royal Colleges, the British Dietetic Association and the Faculty of Public Health(FPH), would reduce the number of British adults who are obese by 180,000 (1.3%) and who are overweight by 285,000 (0.9%), saving the NHS £39m.

“Damage to children’s health should be a major concern,” said Dr John Middleton, vice president for health policy at the FPH. “Sugar is used to pacify, entertain and reward children, but those uses are wiped out by the children hospitalised for dental decay each week. There are nine teaspoons of sugar per can of Coke and this is rising wit h ever-increasing, American-style drink sizes. Coca-Cola is the flagship for sugar marketing and therefore the flagship for rotten teeth and diabetes.

“They’re buying respectability and visibility in all aspects of public life by offering peanuts to cash-strapped local authorities to sponsor their parks – now taking over a high-visibility international tourist attraction and a major icon of the London landscape.”

Professor Simon Capewell from the University of Liverpool, who sits as vice president elect at the FPH, added that the deal was “scandalous”. “People no longer tolerate sponsorship by tobacco companies. Why on earth should we tolerate sponsorship by a sugary drinks company?” he said.

Labour MP and London mayoral hopeful David Lammy said: “Is nothing sacred? Does London really need its modern icon to be emblazoned with the corporate identity of a drink manufacturer? ”

Merlin Entertainment, which owns the London Eye, along with other London attractions such as Madame Tussuads and the London Dungeon, says that Coca-Cola’s relationship with health is not a concern. Sahrette Saayman, Merlin’s communications officer, said: “Our customers are free to consume what they want. Our business is all about giving them a great time when they’re at the London Eye. Our big value has always been to create happy moments for our customers. That’s also been Coke’s values for the last 127 years. Coca-Cola will bring fun activities to the London Eye, which is something we’re looking forward to and delighted about.”

One customer, Suzie Corrigan, who was visiting the Eye on Saturday with her three children aged seven, 10 and 11, disagreed. “They should try and get someone promoting healthy food and activities,” she said. “Coca-Cola is such a well-known brand. To have it in your face as much as it is here is setting a bad example to children, just like smoking would. We need to teach kids about the benefits of healthy lifestyles, which includes cutting out the sugar from our diets.”

Martin Donnelly, who was at the Eye with his three-year-old and six-month-old, said he wasn’t too concerned about the sponsorship deal. “No matter who sponsors the London Eye, somebody somewhere is going to be offended,” he said. “When it was sponsored by British Airways, and later EDF, people who disagreed with climate change were unhappy. You bring it to your common sense. Coca-Cola might be sponsoring the London Eye, but that doesn’t mean I will allow my kids to drink Coca Cola.”

Coca-Cola Great Britain said: “All of our drinks can be enjoyed as part of a balanced diet and we have taken a number of actions to help people choose the best drink for them and their families. These include signing up to the government’s responsibility deal and committing to reduce the calories in our drinks, adopting traffic light labelling to provide consumers with simple and clear nutritional information, reformulating many of our brands to reduce their sugar and calorie content and launching smaller packs like our 250ml can.”

For Dr Middleton, there’s not much politicians can do to prevent unhealthy eating and drinking, “but there needs to be a much bigger public debate about control of advertising before commercial corporate interests infiltrate every aspect of the public landscape,” he said. “What next? Buckingham Palace sponsored by Coca-Cola?”