Emmanuel Macron’s grip on the French presidency looked increasingly shambolic on Wednesday after he was forced to accept the resignation overnight of his interior minister, one of his staunchest allies.

In the latest humiliating blow to France's centrist president, who is facing a nightmarish return from the summer recess, Gérard Collomb, 71, left the interior ministry on foot on Wednesday morning just 24 hours after Mr Macron had refused to allow his once loyal ally to quit.

He was officially replaced by Edouard Philippe, the prime minister.

Mr Collomb, one of the pillars of the Macron administration, had previously let it be known that he planned to leave the interior ministry next May to run for his old job as mayor of the city of Lyon.

But he came under pressure to step down immediately as critics argued it was untenable to run such a powerful ministry while preparing for the campaign trail.

"Considering the rumours and the pressure, I don't want the fact I will be a candidate somewhere tomorrow to affect the way forward for the interior ministry," he said.

His announcement setting the countdown to his departure had already been seen as a direct challenge to the authority of Mr Macron, some 31-years his junior and who Mr Collomb has previously said was like a son to him. Under the French constitution, the president names and removes ministers upon instructions from the premier, not the ministers themselves.