French President Emmanuel Macron's political allies are warning against complacency in the upcoming second-round vote, with all of them saying that the incumbent is not certain to win.

French Prime Minister Jean Castex told French radio on Tuesday, just five days before the elections are scheduled to take place on Sunday, that the French people still need to be convinced that Emmanuel Macron's programs are the best for France.

“We have to convince the French that Emmanuel Macron’s programmes are the best for France and for them. Emmanuel Macron and Marine Le Pen are being put on the same level, but there are enormous differences between them.”

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Castex's predecessor, Edouard Philippe, who polls show is the most popular politician in France, also said there are too many election "unknowns", namely a possible low turnout on election day, in an interview with Le Figaro.

Another powerful Macron backer, François Bayrou, told La République des Pyrénées that either candidate could win at this stage. "Everything is possible. We have all seen voters make choices historians later consider crazy.”

Macron himself was clear he did not consider the election already won. In an interview with TV show C à vous: “Think back to what British citizens were saying hours before the Brexit referendum, or in the US before the Trump vote came: ‘I’m not voting. What’s the point?’ I can tell you, the next day they regretted it. If you want to avoid the unthinkable or something that revolts you, choose for yourself.”

France's Finance Minister, Bruno Le Maire, told Europe 1 radio on Tuesday that Le Pen would  “hand France’s sovereignty to Vladimir Putin”, citing her admiration for Russia and loans she had taken out from Russian banks.

“I heard Marine Le Pen’s international policy proposals… This is the end of French sovereignty,” Le Maire said.

Macron and Le Pen will have a live debate on Wednesday evening.