Paris(CNN) After months of simmering tensions between Rome and Paris, the battle for the soul of Europe just got a lot uglier. On Thursday, France recalled its ambassador to Rome for the first time since 1940, when fascist leader Benito Mussolini declared war. This time the French foreign ministry blamed a war of words -- "the repeated accusations, baseless attacks and outlandish claims" of Italy's populist government.
The barbs between Italy's populist politician Matteo Salvini and the French President Emmanuel Macron have been regular and personal. Last month Italy's far-right Interior Minister and Deputy Prime Minister said he hoped the French people would soon manage to rid themselves of a "terrible president." Macron, for his part, has likened rising nationalism to leprosy, declaring that if the populist nationalists regard him as their enemy, "they are right."
But the straw that appears to have broken the camel's back came in the shape of a meeting between Italy's other deputy PM Luigi Di Maio and France's own populists, the yellow vests. The meeting, which took place on Tuesday on the outskirts of Paris, led Di Maio to declare that the winds of change had now crossed the Alps.
Following France's decision to recall its ambassador, Di Maio tried to justify the meeting. "I wanted to meet with representatives of the 'yellow vests' and the citizens' initiative referendum group, because I do not believe that the future of European politics lies in the parties of the right or the left," Di Maio, leader of the populist Five Star Movement, wrote in a letter published in Le Monde.
The diplomatic row now threatens to spill over into the world of art. Leonardo da Vinci's legacy -- long a source of friction between Italy, where the renaissance master spent most of his life, and France, where he sought refuge and died -- is now being fought over all the more viciously.
The Louvre -- where da Vinci's most famous work, the Mona Lisa, is admired by some 20,000 people a day -- is planning an exhibition in October to mark the 500th anniversary of his death. Rome was due to lend, among other works, da Vinci's famous Vitruvian Man, known by all but seen by few as it is not ordinarily exposed. Italy's junior culture minister, Lucia Borgonzoni, has now threatened to cancel the loan, adding, "there are plenty of things in the Louvre that should be returned to us, even above and beyond the old controversy surrounding the Mona Lisa."
The former Italian Prime Minister, Enrico Letta, who has given up practicing politics in order to teach it in Paris, says that after the last couple of years, nothing surprises him any longer, but he warns that the consequences for both countries could be serious.
"France and Italy are the two superpowers of culture in Europe. We need to work together on big issues. The world has become much bigger than it was. Today, the world is enormous, Italy and France, European counties need to work together -- this is why this fight is really madness," Letta told CNN.
It is no surprise that the origin of the dispute was immigration. The first salvos were launched at the height of the crisis over the rescue boat Aquarius last summer. The vessel, used by SOS Méditerranée to pick up migrants from the Mediterranean, was prevented by the incoming populist Italian government from docking in the Sicilian ports that it had been using for years.
Italy had long argued that it was being made to pick up the tab of Europe's migrant crisis alone, complaints that seemed to fall on deaf ears. The populists decided to strike hard, which led the French president to accuse them of acting "cynically and irresponsibly."
Equally, says Letta, it is no surprise that the row has only escalated now. With just a few weeks to go before European elections, Letta says, "you have to consider the way Macron was elected. He was elected as a shield against a big populist, [far-right politician Marine] Le Pen. The same divide that was successful for him in France, he believes can be successful for him in Europe."
As for the populists in power in Rome, Letta says, "their usual way to is to build up an enemy -- without the enemy you can't be successful when you are populist so for them Macron is the perfect enemy -- perfect target -- they're trying to develop this narrative."
All this means that at least until the May elections, a reconciliation is unlikely. Afterwards, much will depend on the political landscape that emerges in Strasbourg and the relative weight of the populists and those who oppose them.
The row may now threaten the future of Europe itself.