The union leader heading protests against France’s bitterly contested pension reforms has accused Emmanuel Macron of playing with fire and showing contempt for the country’s workers.

Philippe Martinez, head of the powerful CGT, said the president and his government were “disconnected” from the real world, and their advisers needed to “shake the hands of a few who actually work”.

He defended electricity workers who pulled the plug on homes and businesses last week, warning that forcing pension reforms through against public opposition could boost the far right. “People are angry to say the very least, especially young workers who believe their entire generation is being sacrificed,” Martinez said. “Mr Macron is so sure of himself, but he’s playing with fire. We’ve already had Le Pens – father and daughter – twice in the second round of a presidential election.”

Martinez was speaking as ministers approved the reform bill on Friday paving the way for its introduction to parliament next month, and demonstrators took to the streets again in a show of defiance following last week’s return to work by transport staff after a record six-week strike.

The Council of State, the government’s legal adviser, has also criticised the reform law as “imprecise” and “patchy”, and said that it had been given insufficient time to study the bill.

Martinez’s warning echoes that of Jean Grosset, of the left-leaning thinktank Jean Jaurès Foundation, who told the Observer in December: “If there’s no dialogue, no attempt to compromise, just force, it will leave traces of rancour in the country, which [the government] will pay for one day or another, most likely through the ballot box.”

Sitting in the conference room of the CGT’s headquarters near the périphérique ring road east of Paris after returning from the protests on the back of a motorbike, Martinez insisted that the union, the oldest, second-biggest and most powerful in France, was on the right side of the pension dispute.

“We’re not the villainous little Gaulois the president says we are,” he says. “We’ve been called militant and not reformist, but I dispute these labels. We are not against reform, we want it but not this reform.

“We believe we can improve the current system and have made many proposals, but this government doesn’t negotiate. We have a president who thinks he’s always right so it’s difficult to discuss anything. And when discussions don’t work, there are conflicts.”

Union leader Philippe Martinez. Photograph: Gonzalo Fuentes/Reuters

Martinez is the diminutive but formidable figurehead of French unionism. His instantly recognisable face, with drooping moustache, is usually portrayed scowling, belying a dry humour. It has appeared on news kiosks and recent magazine covers as the face of the man who wants to “ruin France”.

In 2016 he was spearheading strikes, blockades and demonstrations against changes to labour laws pushed through by the then Socialist president, François Hollande. Back then he was headlined “the man who wants to bring France to its knees”. Then, as now, there were weeks of protests and industrial action. The labour law was eventually passed.

Half-Spanish through his mother, Martinez has led the CGT since 2015. He has many nicknames – Asterix, Super Mario – and has been likened to General Tapioca in Tintin, none of which particularly bothers him. Hate mail, including an anonymous letter reading “Dirty Spaniard, go back home”, is batted away. Being likened to a terrorist is harder to stomach.

“When an MP from the governing party compares the actions of the CGT to terrorism on the fifth anniversary of the Charlie Hebdo assassinations, when a magazine opinion writer compares you to Daesh [Islamic State], that’s throwing oil on the fire,” he says angrily. “Ministers and MPs need to calm things down, not be insulting and disrespectful.”

Martinez was always going to be Macron’s nemesis. His position on the proposed reforms has never wavered: it is, in a word, “non”. Making French workers work longer is, in another word, “unacceptable”, he says.

“This reform has to be withdrawn because it’s unfair, it’s complicated, and the more the government tries to explain the less people understand,” says Martinez. “People understand one thing: they will have to work until at least 64 years old if they want a decent pension,” he said. “They can leave at 62 if they want to live under a bridge.”

Martinez supports what the union calls “innovative actions” – and the government calls “sabotage” – that saw electricity workers cut supplies to tens of thousands of homes and businesses and shut down France’s biggest hydroelectric centre, despite admitting that this was “illegal”. He did expressly condemn recent wildcat attacks on a rival union, the CFDT, whose offices were raided by CGT members after members voted to call off their strikes.

“I have no problem when actions are targeted and in general we target big companies,” he says.

We’ll keep fighting until they start listening Marie, careworker

“Strikes cause problems. When you have 50 days of protests with a government that is contemptuous of strikers, insults them, arrests them, holds them in custody, then obviously dialogue becomes more complicated.”

He adds: “Mr Macron cannot have it both ways. He cannot invite business leaders to Versailles and vaunt the fact that France is the best country for foreign investment, then say France is always on strike.

Opinion polls may show Martinez only slightly more popular than Macron, but back on the streets he is, like Asterix, the people’s hero.

“Are the government really expecting a carpenter or roofer or mason to work until they’re 64? It’s a catastrophe, of course it has to be withdrawn,” said Jacques, a builder.

“We’ll keep fighting until they start listening,” added careworker Marie, wearing a CGT sticker and with a group brandishing placards showing Macron with a crown. That might be some time, warns Martinez, whose union has called for three more days of action this week.

“It’s quite fashionable to blame the CGT for the ills of the world, but if you’re president of a country where there have been more than 50 days of strikes and protests and polls suggest a majority of people don’t like you, but you still won’t talk – I think I know who’s being obstinate.”

Pension reforms – how will they work?

The French pension system works by “repartition” meaning that those in employment pay contributions to fund those who have retired – which functions when workers outnumber pensioners.

With an ageing population, the government argues that reforms are necessary to balance the books in the future and make the system fairer to groups of workers, including women, who are penalised under the present scheme. The official retirement age is 62, but those in particularly onerous or wearing jobs can retire earlier on a full pension, bringing the average retirement age down to 60, according to the OECD.

The new law replaces the country’s 42 pension schemes with one universal points-based system, that is the same for everyone except those in especially difficult and wearing jobs. The proposed reforms retain the legal retirement age of 62, but encourage workers to stay in jobs longer if they want a full pension.

The government unveiled the changes after a two-year consultation, but the issue has been handled badly, alienating even reform-minded unions, and poorly explained.