France and Italy have continued their unprecedented war of words, with Paris defending its decision to recall its ambassador to Rome, attacking the “nationalist leprosy” eating away at Europe and insisting “playtime is over”.

Italy’s deputy prime minister, Luigi Di Maio, accused successive French governments of pursuing ultra-liberal policies that have “increased citizens’ insecurity and sharply reduced spending power”, and renewed his backing for the country’s gilets jaunes (yellow vest) protest movement.

The French government spokesman Benjamin Griveaux said the symbolic recall of the ambassador to Rome, the first since Italy declared war on France in June 1940, was a temporary measure, but he restated Paris’s case.

“It was important to make a statement, because Italy is a historic ally and also a founding member of the European Union,” Griveaux said on Friday, adding that the decision was prompted by months of “unfounded attacks” from the leaders of Italy’s anti-establishment populist Five Star Movement (M5S) and far-right League.

France’s European affairs minister, Nathalie Loiseau, said Thursday’s move was “not about being dramatic” but about making clear that neighbours, allies and important trading partners should not interfere in each other’s domestic affairs.

“It’s about saying ‘playtime is over’,” she said. “The first thing for a government to do is to look after its people’s welfare.”

Italy’s two deputy prime ministers, Di Maio, of M5S and Matteo Salvini, of the League, have launched a series of increasingly personal attacks on the French president, Emmanuel Macron, who is attempting to rally Europe’s liberals against populist nationalists gaining ground across the continent.

What mainly seems to have infuriated Paris is Di Maio’s unannounced meeting south of Paris this week with a particularly radical member of the gilets jaunes who in December demanded Macron and the government resign and be replaced by a former army chief.

“The most basic courtesy would be to notify the government,” Griveaux said of the visit, which was a surprise even to Italy’s foreign ministry. In a swipe at Italy’s ailing economy, he added that “snide remarks” from Salvini – who has called Macron “a terrible president” – and Di Maio “have not stopped Italy falling into recession”.

Griveaux also repeated a highly controversial phrase used by Macron last summer, comparing anti-immigration, nationalist populism to leprosy: “What is of interest to me is that people in Europe do better, and that we can beat back the nationalist leprosy, populism, the mistrust of Europe,” he said.

On Friday, Salvini, who is also Italy’s interior minister, told a rally for elections in the central region of Abruzzo this weekend that he would issue a formal invitation to his French counterpart, Christophe Castaner, to visit Rome next week, the Italian news agency Ansa reported. “I will summon him because I want to resolve the situation.”

Salvini said he wanted to discuss a number of issues, including France’s efforts to move migrants back into Italy, lengthy border checks, and the return of 15 Italian leftist militants wanted by Rome who have taken refuge in France in recent decades.

Di Maio said in a letter to the French newspaper Le Monde that the French and Italian governments’ current “differences in policies and vision” must not be allowed to “affect the historic friendship that unites our two peoples and two states”. He reaffirmed Rome’s “willingness to collaborate”.

However, Salvini’s interior ministry issued a statement saying France was no longer willing to take in some of the 47 migrants stranded on a rescue ship off Sicily for two weeks in January, as it had originally promised, offering instead to help Italy establish repatriation deals with African countries.

“Not even France wants illegal immigrants,” the statement said. “We now wait for Paris to demonstrate its good will with acts and to begin collaborating in order to repatriate from Italy the many [African migrants] who are here illegally.”

Italy’s transport minister, Danilo Toninelli, upped the ante, saying gilets jaunes protesters were welcome to use the M5S online portal and technical advice to help them build a citizen’s movement. “We can offer them a hand and do political activities in service of the French people,” he said.

The two countries’ business lobbies, Cofindustria and Medef, called for constructive dialogue to resolve the dispute, while the Italian president, Sergio Mattarella, said Italy’s friendship with France needed to be “preserved and defended”.

The dispute has prompted concern among analysts and diplomats. “It doesn’t surprise me,” Marc Lazar, a professor at Sciences Po in Paris, told Le Monde. “Franco-Italian relations are now undergoing their most serious crisis since 1945; bilateral tensions have been increasing for months.”

Diplomats say Paris believes Salvini and Di Maio are electioneering before May’s European elections, creating and exploiting disagreements in order to undermine the pro-European Macron.

But with Brexit looming and worsening east-west divides, analysts wonder about the consequences for the Europe Union.

“The fact that we can’t work with Italy on the European project is a real problem,” said Sebastien Maillard, of the Jacques Delors Institute thinktank in Brussels. One former diplomat, who asked not to be named, said the real problem “is not Italy’s relationship with France, but Italy’s relationship with Europe”.

Additional reporting by Angela Giuffrida in Rome