Prince Charles was attending the launch of a public health awareness campaign aimed at fighting diabetes in the United Arab Emirates (UAE).
He visited the Imperial College London Diabetes Centre and watched as a group of children chose from a selection of “good” and “bad” snacks for their school packed lunches.
Talking to Nadine Tayara, a nutritionist from the centre who had put the children through their paces, he asked her: “Have you got anywhere with McDonald’s? Have you tried getting it banned? That’s the key.”
A McDonald’s spokeswoman said that Charles’s remark was “disappointing”.
Other members of his family had visited the fast-food chain, she said, and “have probably got a more up-to-date picture of us.”
The spokeswoman added: “This appears to be an off-the-cuff remark, in our opinion. It does not reflect our menu or where we are as a business.”
Charles was clearly unaware of some of the moves the company has made, she said, such as improved labelling, supporting sustainable agriculture and nutritional changes with choice and variety.
She said that their food would fit into any balanced diet.
In August 2005 Prince Harry popped into a McDonald's for a "buy one get one free" meal. He is reported to have bought two chicken burgers and a strawberry milkshake, eating the meal on the pavement outside.
And in January 1992, when Prince William was nine, he was pictured with his mother queuing up for a burger at McDonald’s.
A Clarence House spokesman, travelling with the Prince and Duchess on their 10-day tour of the Gulf, later issued a statement.
It said: “The Prince of Wales has for a long time advocated the importance of a balanced diet, especially for children.
“In visiting the diabetes centre today, he was keen to emphasise the need for children to enjoy the widest variety of food and not to eat any particular sort of food to excess.”
Encouraging pupils to eat sensibly is one of the initiatives of the campaign - Diabetes Knowledge Action - and it is hoped the UAE children will pass the healthy eating habits on to their families.
When all the children picked up bottles of water and tiny bags containing fruit and vegetables, ignoring crisps and chocolate the Royal couple laughed.
Prince Charles, who was visiting the centre with the Duchess of Cornwall, is a keen advocate of organic food and in 1986 set up a farm on his Highgrove Estate that does not use artificial pesticides of fertilisers.
The UAE has the second highest prevalence of diabetes in the world with more than 20 per cent of those aged 20-79 already diagnosed with the illness, while 40 per cent of the population are prone to the disease.