McDonald’s has been accused of launching a “grotesque marketing strategy” that endangers public health by encouraging customers to eat more fast food in exchange for prizes such as fries, desserts and fizzy drinks.

Tom Watson, the shadow culture, media and sport secretary, has urged the company to ditch its Monopoly at McDonald’s promotion in light of the childhood obesity crisis in the UK, branding the competition “a danger to public health”. His demand comes as the government tries to tackle childhood obesity with a plan to reduce the amount of advertising for foods high in fat, sugar and salt seen by children. Options being examined include a ban on such adverts on television, online streaming sites and social media until after the 9pm watershed.

It follows research suggesting children are spending 14 hours a week watching television and an increasing amount of time online. One in three children are overweight or obese and the number of severely obese children is on the rise. The UK has one of the worst records in western Europe.

Watson has written to McDonald’s UK chief executive Paul Pomroy calling for the forthcoming Monopoly promotion to be cancelled. “The UK has an obesity crisis,” he writes. “Almost two-thirds of adults in England are overweight or obese. A quarter of children in England are overweight or obese by age five, rising to over a third by the end of primary school. Obesity and a sugar-filled diet cause a variety of serious health conditions, including Type 2 diabetes which costs the NHS 10% of its budget every year to treat.

“In this context, it is appalling that your company’s Monopoly marketing ploy encourages people to eat more unhealthy foods by offering sugar-filled desserts as rewards.

As a society we have a responsibility to safeguard the health of our children Tom Watson MP

“It is unacceptable that this campaign aims to manipulate families into ordering junk food more frequently and in bigger portions, in the faint hope of winning a holiday, a car, or a cash prize many would otherwise struggle to afford.”

Watson said poor children were affected more because research suggested that 39% of McDonald’s restaurants are in the UK’s poorest areas. “It is clear that McDonald’s Monopoly is a danger to public health,” he writes. “Businesses have a moral responsibility to their customers, and as a society we have a responsibility to safeguard the health of our children.

“I am requesting that you urgently rethink this strategy: McDonald’s must stop playing on people’s hopes and prioritising profit over public health. I urge you to cancel this marketing campaign.”

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A McDonald’s spokesperson said: “Customer choice is at the heart of everything we do, including our popular Monopoly promotion. This year’s campaign sees customers receive prize labels on carrot bags, salads and our Big Flavour Wraps range, and we have removed the incentive to ‘go large’, providing the same number of prize labels and chances to win on a medium meal as you get on a large.

“Nutrition information is clearly displayed online, on our app, in restaurant and across our packaging and we continue to review, refine and reformulate our menu to reduce saturated fat, salt and sugar.”

A recent report found that almost 20% of deaths worldwide are attributable to an unhealthy diet, ranking alongside high blood pressure and smoking as the top three risk factors.