Environment Minister Mr Hulot resigned from president Emmanuel Macron‘s cabinet during a bombshell live radio interview.
He cited an “accumulation of disappointments” over green issues including the 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.
Mr Hulot was known to be furious at the government’s vow to relax hunting laws in a bid to a boost Mr Macron’s appeal in rural areas.
The environmentalist also attacked Mr Macron’s decision to “persist” in a nuclear industry that is a “useless madness, economically and technically”.
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.
“I would have liked him to stay because he brought his own voice, his own convictions and his commitment. I regret his departure.”
French president Mr Macron has spent much of this summer embroiled in a scandal involving his ex-bodyguard Alexandre Benalla.
Shocking footage emerged last month of Mr Benalla, wearing police riot gear, assaulting protesters at May Day protests in Paris.
He was later fired and placed under investigation, but political opponents said Mr Macron was slow to react to the scandal.
Critics accused the president of a cover-up by claiming he failed to report the incident as soon as he was made aware of it.
The 40-year-old leader survived two no-confidence motions put forward by opposition MPs last month.
But the ex-banker faces further political turmoil as he embarks on a new wave of controversial reforms in the coming weeks.
Mr Macron has vowed to reform France’s pensions system, overhaul public healthcare and shake-up the highly unionised public sector.
But his reform drive will be complicated by forecasts that France economic growth is slower than expected.
The economy eked out less growth than expected in the second quarter of the year as strikes and higher taxes hit consumer spending.