Italy’s Prime Minister Giorgia Meloni described France’s government as “aggressive” and “incomprehensible” after it chastised Italy for refusing to dock a migrant ship.
Italy recently accepted three NGO boats rescuing migrants crossing from Libya after previously blocking them.
It also stated that France had agreed to accept another ship, the Ocean Viking.
That announcement drew applause from Italy’s Deputy Prime Minister Matteo Salvini, who declared that “the air has changed.”
Also Hungary’s far-right leader Viktor Orban thanked Ms Meloni for “protecting Europe’s borders”.
But reports suggest French authorities had not actually agreed to a deal.
In Paris, Italy’s public announcement is being seen as a way of forcing it into accepting the boat.
French Interior Minister Gérald Darmanin said France would exceptionally let the Ocean Viking dock – with the ship arriving in Toulon on Friday morning.
But he described Italy’s actions as reprehensible and selfish, warning of “very serious consequences”.
In a press conference on Friday, Ms Meloni said she was struck by France’s “aggressive reaction” which she also described as unjustified.
The comments come amid an increasingly explosive war of words between the two European Union members over migration, on which Italy’s new right-wing government has vowed to clamp down.
France has now suspended an agreement to take in 3,500 migrants relocated from Italy, urged other EU members to do the same and tightened controls on its borders with Italy.
Ms Meloni has warned it would not be “intelligent” for the EU to isolate Italy.
She stressed that her country had taken in almost 90,000 migrants this year, while Ocean Viking, with 234 on board, was the first NGO rescue boat that France had ever accepted.
“The situation cannot continue this way,” she added, saying that France’s reaction had betrayed a lack of European solidarity.
The unequal burden-sharing of migration has long caused friction within the EU, and Italy, Greece and Spain and have argued that they cannot be expected to shoulder the weight.
Domestic politics has also fed into the row – on both sides of the border.
Italy’s prime minister – the country’s first far-right leader since World War Two – campaigned on halting migrant boats and needs to please her electoral base.
In France, President Emmanuel Macron faces pressure from the far-right’s National Rally, whose leader Marine Le Pen has been quick to capitalise on the issue.
She accused Emmanuel Macron of “dramatic laxity” by accepting the ship, denouncing his failure to stop “massive and anarchic immigration”.
Whatever the motive, the result is now the worst crisis between France and Italy since 2019, when the then Italian deputy prime minister paid a solidarity visit to the anti-government gilets jaunes (yellow vest) protesters in France, prompting Paris to withdraw its ambassador to Rome.
It is rare for western EU members to criticise each other so openly – and does not bode well for relations between Italy’s new government and its traditional allies.