"I say to Europeans: Wake up. Wake up! They are hidden Brexiteers. All European nationalists are hidden Brexiteers. It's all the same lies," he said.
"Make no mistake. If you entrust the keys to people who think like they do, there is no reason why Europe should become a great power," he said.
"In a way it's as if we were saying it's not a problem if we entrust the bank to robbers. When they are around the table, they take Europe hostage."
Macron gave the example of the French far-right Rassemblement National (RN) party, which is now leading in opinion polls for the European contest, ahead of his own centrist alliance.
The RN "wanted to pull out of Europe, out of the euro, out of everything," he said.
"Now it no longer says anything. It's reaping the benefits of Europe, while wanting to destroy it without saying anything.
"And that's true in every country," he added.
He noted that Italian Prime Minister Giorgia Meloni, whose Brothers of Italy party has neo-fascist roots, had "a European approach" and had "supported the asylum and immigration pact".
But "after that, the best way of building together is to have as few nationalists as possible", he added.
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