Ten o'clock on a starless summer night. The end of the late day shift at a giant factory complex abutting this picturesque market town south of the river Po. Either side of the gates stretches a smooth, unscaleable 10ft wall.

A worker in a red polo shirt and beige shorts awaits one of the buses the company lays on to take its employees back to their villages in the surrounding hills. He works in "Experimental", he says.

For weeks now, the product manufactured in the factory has been at the centre of a fierce controversy stemming from fear that draft European regulations aimed at fighting obesity will have a detrimental impact on their favourite treat. It was the scale of the country's reaction which on Tuesday prompted the European parliament to issue a statement denying any plans to ban it.

The worker denied knowledge of the row. He had only good words for his employers, whose company was "wholesome, honest and respectful". But when asked his name, he replied: "Better I remain anonymous."

It may seem odd that such secrecy should be applied to the manufacturing of a hugely popular chocolate and hazelnut spread that many Europeans, and particularly Italians, regard as the ultimate in comfort food.

"What world would this be without Nutella?" asks an advertisement, raising a spectre which, on 16 June, it suddenly declared was real. Francesco Paolo Fulci, the vice-president of the Ferrero group, said new regulations approved by the European parliament, which have yet to be endorsed by the council of ministers, could put Nutella "outside the law".

In Italy, Ferrero's paste has acquired a status that moved one writer to describe as "national Nutella". A reminder of childhood indulgence, it has figured in songs, novels, paintings and films. In the run-up to the World Cup, the national squad's chef assured viewers of Italian TV ads that he served Ferrero's gloop to the team for breakfast.

Amid newspaper headlines about a "Battle for Nutella", a prominent Northern League politician announced the setting up a "Hands off Nutella" committee and ministers in Silvio Berlusconi's cabinet assured the public the government was doing everything in its power to safeguard the spread.

This week's statement was greeted with relief. "I am truly happy," said the agriculture minister, Giancarlo Galan. The European parliament's reassurance would give "joy to adults and children".

The hullaballoo may have served to demonstrate the awe-inspiring degree of loyalty enjoyed by Nutella (and Ferrero's political leverage ). But it also turned a spotlight on the methods of one of the world's most secretive firms.

Ferrero, which also makes Kinder eggs and bars, Mon Chéri and Ferrero Rocher chocolates and Tic Tac mints, has never held a press conference, even to announce its annual results. Its joint chief executives – the sons of the group's octogenarian patriarch, Michele Ferrero – have only once given an interview.

Asked by the Guardian for a tour of the Alba plant, a spokesman replied: "It is not possible either to visit it or film it." Would it then be possible to speak to an executive? "That will be very difficult". Two subsequent emails went unacknowledged.

A senior company source – "Don't quote me by name, I beg of you" – suggested the ban on tours was a precaution against industrial espionage. "It's like Nasa," said the source.

Such was the emphasis on secrecy that Ferrero's products were made with machines built by the company's own, in-house engineering department.

Nutella is based on a local speciality, gianduia, a blend of chocolate and nut paste said to have been invented to compensate for the scarcity of cocoa brought about by Napoleon's blockade of Britain and its colonies. The first jar of Nutella was sold in 1964 after Michele Ferrero modified his father's recipe.

His family members are still the firm's only shareholders and two years ago, Michele overtook Berlusconi to become Italy's richest citizen. Forbes put his immediate family's wealth at €9.5bn.

Though locals say Michele still banters with older employees in broad dialect, he now divides his time between Alba and Monte Carlo, where the source confirmed he had a private laboratory. "The part he loves is the creation of products," said a local acquaintance.

Usually seen in public in dark glasses, apparently because of an eye complaint, Michele Ferrero is reputedly a devout Catholic who has infused the group with a strong sense of social responsibility.

Claudio Risso, who worked at the Alba plant before becoming a national official of the CISL trade union federation, said management believed in "a sort of participatory democracy". It had "very good" relations with the unions, who had never called a strike.

This all sits oddly with its latest, uncharacteristically high-profile initiative, for as the company acknowledged in a message to consumers on 21 June, there never was a threat to Nutella.

The plans endorsed by the European parliament, which Ferrero's vice-president called a "straitjacket", would merely oblige manufacturers to label food with a "nutritional profile" showing the proportions of ingredients such as sugars, fats and salt — something Ferrero claims it already does.

The Italian press suggested it was worried about a provision that would stop makers of high-fat, high-sugar products promoting them as elements in a healthy lifestyle. But without denying that assertion, Ferrero's message said the vote "had not had any impact on Nutella's present advertising".

Its real concern, it said, was that "Brussels' approach … could lead to curbs on even the most private behaviour" – an explanation as cryptic as that given by the retiring Michele Ferrero in his only known statement to the media.

In 1996, he was ambushed by a TV crew on his way into a conference. What, the reporter asked, was the secret of Ferrero's success? Without breaking pace he replied: "Our Lady of Lourdes".