Ukraine’s fall would cause a tidal wave of “10 million migrants” fleeing to Europe, France has warned, adding that it has seen evidence that Russia “won’t stop” at its conquest of the country.

Speaking to France Inter radio, Stéphane Séjourné, the French foreign minister, said: “First of all, there is a risk of Ukraine collapsing and there are consequences to this risk.

“We’re talking about 10 million Ukrainians who could leave Ukraine in the event of a collapse. And we know very well, and have information, that Russia will not stop there.”

Mr Séjourné singled out Moldova as Vladimir Putin’s next target.

The warning over a possible flood of refugees to the West appeared to be aimed at the French hard-Right, whose placatory tone towards Russia, Mr Séjourné implied, could see France facing mass migration. This is a major concern for Marine Le Pen’s National Rally, which is polling to come first in European elections in June.

“Everything we are doing is to avoid war,” he said.

The comments came a day after Putin threatened nuclear conflict should the West send ground troops to help the country Russia invaded.

Earlier this week, Emmanuel Macron, the president, refused to rule out the deployment of Western ground troops, sparking unease amongst his allies gathered in Paris. Almost all of them distanced themselves from the remarks.

Mr Séjourné warned would-be appeasers, notably the French hard-Right, that the West was facing a new Munich Agreement. He was referring to the 1938 deal between UK, France and Fascist Italy that allowed Germany to annex part of Czechoslovakia in the vain hope it would quench Hitler’s imperialist ambitions. It has since become the byword for failed appeasement.

“We cannot find ourselves in the same period as September 1938, when Czechoslovakia was abandoned for a short-lived peace in the Sudetenland,” he said, referring to the territory where more than three million people, mainly ethnic Germans, lived.

Mr Séjourné denied that Mr Macron’s suggestion of ground troops was a mistake given the reaction of his allies. “A very clear framework has been set, namely to put Russia in check without going to war with Russia. And within that framework, nothing is ruled out.

“It contributes to strategic ambiguity, but at the same time it puts us on the right side of history. I’m very happy with it.”

As for Mr Putin’s nuclear threat, he said this was nothing new. “When we decided to send military equipment, he raised the nuclear threat. When we decided to send tanks, he raised the nuclear threat. When we decided to send planes, he raised the nuclear threat,” he said.

“So now we’re taking it to the next level, ruling out anything, and he’s raising the nuclear threat.”

Mr Séjourné said that the French president’s comments were justified because Russia had changed its “stance” and was already “attacking France” and Europe.

“We are in a fragile situation with the preparations for the European elections and the Olympic Games… It’s their services, our public services, our transport, our hospitals. Imagine for two minutes that we had no hospitals in the Paris region, that transport came to a standstill because of Russian computer attacks. All this means that Russia has changed its stance,” he said.

He then issued a thinly veiled broadside at Ms Le Pen, who has long been close to Mr Putin and who this week accused Mr Macron of “taking a further step towards belligerence, posing an existential risk to 70 million French people”.

“Let’s not work with the Kremlin’s language and doctrine,” said Mr Séjourné.

“A number of political parties are playing into Russia’s hands today, either knowingly or unknowingly.”