An explicit sex scene in a newly published novel by the French economy minister has left the government facing fresh accusations it is not listening to the concerns of the country just as it tries to contain anger over the unpopular rise in the pension age.

The toe-curling sexual descriptions in the novel, Fugue Américaine, written by the economy minister, Bruno Le Maire, have angered opposition politicians and inspired anti-government slogans and graffiti at street demonstrations as the government struggles to contain the political crisis over Emmanuel Macron raising the minimum pension age to 64.

The novel was published hours before the credit ratings agency Fitch downgraded the country’s debt worthiness last week, feeding accusations from leftwingers that writing the novel had taken Le Maire’s focus off the economy and inflation.

The minister’s book is a fictionalised account of the pianist Vladimir Horowitz, told through the story of two brothers who travel to Cuba to attend one of his concerts. But it was a sex scene in chapter 11 that has gone viral and prompted French satirists and protesters to ridicule Le Maire.

The public broadcaster France Info said that the sex scene, involving a character called Julia, had been greeted with “mockery and stupefaction”, while the French edition of the Huffington Post headlined its story “Bruno Le Maire has written about an anus and no one was ready for this.”

Julia’s declaration, “I’ve never been this dilated”, sparked ridicule and became the topic of anti-government signs and graffiti at May day demonstrations across France.

The satirist and comedian Sophia Aram read out the sex scene on France’s most popular radio station to a soundtrack of Spandau Ballet music amid jokes about the economy on its knees.

Olivier Varlan, a historian, joked on Twitter that the government should put in place a psychological hotline for people who had stumbled upon the chapter by accident. The award-winning French novelist Nicolas Mathieu, although accepting that any sex scene taken out of context would look ridiculous, offered his own re-writing of the scene.

“At a time when the French people have huge worries about inflation … should he have one minute, one hour, one week of his time to dedicate to writing erotic scenes?” asked the MP François Ruffin of the radical left party, La France Insoumise.

Thomas Portes, of the same party, tweeted: “Inflation is exploding, millions of people can’t eat or fill their fridge, pay their rent. France is fighting the pension reform. And during this time, the minister Bruno Le Maire writes novels. Right to the end, they’re throwing disdain in our face.”

Le Maire’s colleague, the labour minister, Olivier Dussopt, admitted he had not read the novel but defended the minister’s right to write it. “This shows that there are feelings … behind the suits of the ministers,” he told BFMTV, adding that he had read the sex scene and it “made him smile”.

Le Maire, faced with astonishment that he could do a round of media interviews plugging an explicit novel when French people were struggling to make ends meet, hastily explained that writing was his hobby.

“Many of you are asking me how I find the time to write when I’m a minister,” he wrote on social media, explaining that it was his way of finding “personal balance” in life. “Some people do gardening or go hiking, I write,” he said, later explaining on French TV that he wrote in the holidays, at weekends and after getting up at 5am.

Le Maire, who was formerly in the rightwing party of Nicolas Sarkozy and has been economy minister since Macron took office in 2017, has published five books during his time running the French economy.

In a 2004 memoir about his time as a political adviser to the then foreign minister, Dominique de Villepin, Le Maire had also raised eyebrows by writing about his wife touching his penis on a trip to Venice.

The latest row comes amid controversy over the communications of Macron’s government after the social economy minister, Marlène Schiappa, posed for Playboy at the height of demonstrations against Macron’s pensions law. The prime minister, Élisabeth Borne, called Schiappa to tell her that it “was not at all appropriate, especially in the current period”.

The leftwing daily Libération calculated that Le Maire had published more words since taking office as economy minister in 2017 than his close friend, the controversial novelist Michel Houellebecq, in the same period.