French President Emmanuel Macron on Wednesday urged rival parties to join his electoral alliance against Marine Le Pen's far-right National Rally, while the conservative Republicans ditched their party chief for seeking a far-right pact.

The fast-moving political developments come after Macron's shock decision to call a snap parliamentary election in a few weeks' time. The vote could hand real power to Le Pen's party after years on the sidelines.

In what amounted to a campaign speech, Macron on Wednesday defended his decision to call the snap vote, and urged parties on both sides of the political centre to join him in the battle against the hard right in the June 30 and July 7 elections.

Macron, who ruled out quitting if his ruling alliance loses, called on "our compatriots and political leaders who do not recognise themselves in the extremist fever" to "build a new project ... a coalition to govern."

In a sign of the political chaos that Macron's decision has unleashed, the Republicans party leadership on Wednesday decided to kick out their party chief Eric Ciotti after he appealed for an electoral alliance between his party's candidates and the RN.

Macron described such an accord as a "deal with the devil". It would have ended the decades-long mainstream political consensus to block the far-right from power.

Writing on X, Ciotti said the Republicans meeting had not followed protocol: "I am and remain the president of our political party, elected by the members!" he said.

Macron called the election on Sunday after the anti-immigration, eurosceptic RN came out on top in a vote for the European Parliament. (Reuters)