President Emmanuel Macron suffered a major political blow Tuesday as his popular environment minister resigned live on radio - without informing the French leader beforehand.

Nicolas Hulot, one of the most respected members of the cabinet among the French public, took even his interviewers by surprise on the France Inter radio station when announcing his move.

"I am taking the decision to leave the government," Hulot said, adding that he felt "all alone" on environmental issues within the government.

The 62-year-old TV celebrity, who made his name as an environmental campaigner, was lured into government last year by Macron, but has repeatedly clashed with his cabinet colleagues over policy.

"We're taking little steps, and France is doing a lot more than other countries, but are little steps enough?... the answer is no," he added.

Hulot, whose future in the government has been a subject of speculation for months, said he had not informed Macron or Prime Minister Edouard Philippe of his plans to resign.

"It's an honest and responsible decision," he added.

His departure adds to mounting problems for 40-year-old centrist Macron, who swept to power in May last year promising to solve decades of low growth and high unemployment in France and reform the European Union.