The first poll taken after French President Emmanuel Macron announced snap parliamentary elections shows his party will lose badly, potentially forcing him to resign.

Following his trouncing by Marine Le Pen's National Rally in the EU elections, Macron was forced to announce new parliamentary elections, the first round of which will take place on June 30th followed by the final round on July 7th.

Although his presidency is not technically under threat, should Macron receive a similar drubbing, some observers say he would have to step down.

A poll conducted by Harris Interactive for French publication Challenges shows that Macron's Ensemble party would win around 125 to 155 seats.

This would leave Le Pen's party in a position to claim between 235 and 265 seats, meaning they would be able to form a relative majority.

Crucially, the survey was taken before the news broke that National Rally and The Republicans (LR) would form an alliance together, meaning Le Pen's margin of victory is likely to be significantly higher.

Such an alliance would add an extra 40 to 55 seats to Le Pen's total, giving her an absolute majority, strong mandate and putting her in a great position to challenge for the presidency in 2027.

According to political scientist Dominique Moïsi, Macron is likely to lose the gamble he made.

"It's less what he did, than the perception of what he is, i.e., an arrogant, narcissistic person. He is the incarnation of the distant elite in the eyes of many Frenchmen," said the French writer.

On Tuesday, center-right Republicans (LR) leader Éric Ciotti announced that an alliance with Le Pen had been agreed.

"We need an alliance, we are doing it, an alliance with the National Rally, with its candidates. All outgoing Republican deputies who wish not to have an opponent from the RN will not have a competitor," said Ciotti.

"We love France, we believe in authority. The challenge is to straighten out the country," he added.