Environment Minister Mr Hulot resigned from Mr Macron’s cabinet this morning during a bombshell live radio interview.
He cited an «accumulation of disappointments» over green issues including French government’s failure to tackle climate change.
His departure will be a major blow to Mr Macron whose popularity among voters has hit record lows, according to opinion polls.
Mr Hulot said: «We’re taking little steps, and France is doing a lot more than other countries, but are little steps enough? The answer is no.
«My decision comes from an accumulation of disappointments. I don’t have faith in the state any more.
«I don’t want to give the illusion that my presence in the government means we are up to the task of meeting environmental challenges.»
Shortly after his announcement, government spokesman Benjamin Griveaux said he «regretted» Mr Hulot’s exit.
Mr Griveaux said: «I don’t understand why he is stepping down when we had many successes in the first year that are to his credit.
«He didn’t win all his battles but that’s the way it goes for ministers. It’s a blow from which we’ll recover.
Hulot announced his decision to quit after the government said it would relax hunting laws, a measure aimed at boosting Mr Macron’s appeal in rural areas.
In his radio interview, however, he emphasized the inadequacy of «mini steps» taken by France and other nations to slow global warming and avert a collapse of biodiversity.
«I don’t want to create the illusion that we are facing up to it,» he said.
The French president has spent much of this summer embroiled in a crisis involving his ex-bodyguard Alexandre Benalla.