Royal’s Italian counterpart told her to “leave Italian products alone” after she criticised the use of palm oil in the hazelnut spread, which is made by Italian confectionery company Ferrero.

The spat over one of Italy’s most important products came at an already tense moment in Italian-French relations, with a bitter standoff over hundreds of migrants stranded in the Italian border city of Ventimiglia after being denied entry into France.

The migrant issue is likely to be raised in a meeting on Sunday between the Italian prime minister, Matteo Renzi, and François Hollande, the French president, who will be visiting his country’s pavilion at the Milan Expo, where Ferrero is a “major partner”.

Luca Galletti, the Italian environment minister, rushed to Nutella’s defence after Royal said in a television interview that the use of palm oil in the product was leading to “massive deforestation”, which was a cause of global warming.

The edible oil derived from palm fruit is grown throughout Africa, Asia, North America, and South America, though 85% of all palm oil is produced in Indonesia and Malaysia, where swaths of forest have been cleared for plantations. It is used in a wide range of products, from shampoo to ice cream.

“We should stop eating Nutella, for example, because it’s made with palm oil,” Royal said in an interview on Monday night on Canal+. She said the product ought to be made with “other ingredients”.

Galletti retorted: “Ségolène Royal is worrying. Leave Italian products alone. For dinner tonight … it’s bread with Nutella.”

Another senior Italian politician, Michele Anzaldi, demanded an apology from Royal, saying on Twitter that France had committed a “serious and ugly” slight against “Italian excellence”.