Action on Sugar campaigners are urging for freakshakes to be banned, as some can contain 'grotesque levels of sugar and calories' and more than half of an adult's daily calorie allowance.
After looking at the milkshakes sold around the UK, the group found that the Toby Carvery Unicorn Freakshake was the worst offender, with 39 teaspoons of sugar and containing a whooping 1,280 calories.
Action on Sugar chairman Graham MacGregor, professor of Cardiovascular Medicine at London's Queen Mary University, said the government's current efforts to fight the obesity epidemic are not enough.
He said: 'These very high calorie drinks, if consumed on a daily basis, would result in children becoming obese and suffering from tooth decay - that is not acceptable.
'These high calorie milkshakes need to be reduced immediately below 300kcal per serving.'
These are the freakshakes Action on Sugar found to be worst offenders up and down the country:
| Toby Carvery Unicorn Freakshake | 156 | 39 | 1280 |
| Five Guys Milk Shake Base + Banana + Chocolate** | 149 | 37 | 1073 |
| Five Guys Milk Shake Base + Cherry** | 120 | 30 | 975 |
| Pizza Hut Salted Caramel Ice Cream Shake | 95.4 | 24 | 738 |
| Harvester Cookie Monster Freakshake | 95 | 24 | 1067 |
| Toby Carvery Cookie & Chocolate Freakshake | 94 | 24 | 961 |
Registered nutritionist Kawther Hashem, a researcher at Action on Sugar based at Queen Mary, said: 'Undoubtedly some of these milkshakes contribute to excess sugar and calorie intake, and it is shocking this information is hidden from the consumer, who would struggle to find it.
'It is time the government introduced legislation to force companies to be more transparent about what is in their products by displaying clear nutrition information online and in the outlets, at all times.'
Dr Alison Tedstone, chief nutritionist at Public Health England, also added: 'The food and drink industry - including restaurants, manufacturers and retailers - has a key role in helping to tackle this, by reducing the amount of sugar we buy and consume, and we hope to see them step up to the challenge.'
Following the warning, they are calling for compulsory traffic light-coloured nutrition labels to be included in all menus, so that consumers know the nutritional value of what they are ordering, which the government is currently consulting on.
They are also calling for milkshakes that exceeded 300 calories per serving to be banned.
