President Emmanuel Macron suffered a major political blow today 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 63-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.

Due to slowing economic growth, his government is having difficulties drawing up the 2019 budget which saw Prime Minister Philippe announce at the weekend that he was dropping targets for reducing the deficit.

At the diplomatic level, Macron is struggling to convince his European partners of the need for a more integrated EU as nationalist governments make gains across the continent.

Over the summer, the former banker also suffered the first major political scandal of his 15-month term when a senior security aide was filmed manhandling protesters while wearing a police helmet.

Anger in government

Hulot's announcement is likely to be received bitterly by Macron, who was starting a trip to Denmark to sell his EU agenda today.

"The most basic of courtesies would have been to warn the president of the republic and the prime minister," government spokesman Benjamin Griveaux told the BFM news channel.

Hulot was formerly the star presenter of the hit Ushuaia environmental TV programme in France and had repeatedly turned down offers to enter government by previous French presidents.

He was widely reported to be close to quitting in February after media reports that the granddaughter of former French president Francois Mitterrand had accused him of rape in the 1990s.

Hulot furiously denied the claims and said they had been extremely hurtful for him and his family.

He had also faced criticism from fellow green campaigners, who accused him of failing to influence the Macron government sufficiently after he lost battles with his colleagues in the agriculture and economy ministries.

Hulot was left disappointed when the government backtracked on a target to reduce the share of nuclear power in the country's energy mix to 50 percent by 2025, while EU negotiations on pesticides were another source of frustration.

On Monday, the cost of a hunting licence was cut in half to 200 euros -- another bitter pill for the vegetarian.

"Do you do an environmental revolution in one year? The response is no," government spokesman Griveaux added. "I prefer little steps to not moving."

Macron's record on the environment is mixed.

He has made the battle against global warming one of his foreign policy priorities, organising a major conference in Paris last year in an effort to compensate for Trump's scepticism about climate change.

He also led efforts at the EU level to reduce the use of the controversial weedkiller chemical glyphosate and he scrapped a proposed airport in western France, partly on environmental grounds.

Macron's political opponents immediately seized on the resignation.

"I don't necessarily share the same opinions as Nicolas Hulot, but I can understand that he feels betrayed today, like a lot of French people, by the strong promises that were made and the sense that in the end they have not been kept," said Laurent Wauquiez, the head of the rightwing Republicans party.