It’s the gloopy chocolate and hazelnut spread that has become a worldwide food phenomenon, whether slathered on toast or eaten straight from the jar by the spoonful.

But aficionados of Nutella are up in arms after discovering that the recipe has been secretly changed, with more sugar and fat – but fewer hazelnuts.

Ferrero, Nutella's Italian manufacturer, admitted it had carried out "fine-tuning" but insisted the nutritional value of the new version was similar to its predecessor.

The recipe tweaks had been spotted by the eagle-eyed German consumer group Hamburg Consumer Protection Centre and revealed on its Facebook page.

Have appetite, will travel: The rise of food tourism

---

‘I'd get in massive trouble for stealing lobster legs, sucking the meat out like straws’

---

21-year-old Irish woman named ‘Best Young Chef in Europe’

---

‘We took turns to spoon the mixture into the stomach, delighting as its horror film contours grew’

---

It claimed the new recipe has increased the content of powdered skimmed milk from 7.5 per cent to 8.7 per cent, and sugar from 55.9 per cent to 56.3 per cent.

Furious Nutella fans took to Twitter to criticise the changes, using the hashtag #boycottNutella.

@RoshhNosh said: “How dare they tamper with Nutella’s recipe. Leave the chocolatey goodness alone”

@AllesParr tweeted: Not a good idea to mess with #Nutella lovers!

Another wrote: “If the rumours of #Nutella changing their recipe are true, I am boycotting them.”

And another fan said Ferrero “should be reducing sugar content in this day and age”.

In a statement Ferrero confirmed the changes had been made but insisted that “the quality ... and all other aspects of Nutella remain the same”.

The nutritional content of Nutella has not been without controversy. Earlier this year fans were shocked by a “deconstructed” photo of its raw ingredients – shown in layers of a jar – that revealed the high sugar content.

“We are shocked to see Nutella has ramped up the amount of sugar in its already sweet product,” said Kawther Hashem, nutritionist at Action on Sugar.

“Based on their original formulation which has less sugar than the new formula, just two slices of bread with Nutella (24g sugar) contains the entire maximum daily intake of 7 to 10-year-olds. Eaten over the duration of a week that’s 168g of sugar – the equivalent amount found in two and a half boxes of Maltesers (120g box). Nutella is high in sugar and should not be eaten every day.”

Nutella also contains palm oil, which causes concern because of possible links to cancer as well as its damaging environmental impact.

But Ferrero has a robust palm oil charter and says it can trace almost all of its palm oil to sustainable sources. The company came top of a WWF sustainability league table of 137 palm oil buyers last year.

Chocolate fans can be unsettled by tweaks to their favourite products. In November last year the confectionery giant Mondelez sparked uproar by changing the shape of the popular Toblerone bar, a move fans described as "stupid", "ridiculous" and "just plain dumb".

And in 2015 consumers of Cadbury’s Fruit & Nut chocolate bars reacted with fury after the company changed the recipe for the first time in 90 years to include sultanas. Other recent changes to Jaffa Cakes and Walnut Whips have also irked devotees.

- The Guardian