By Henri Astier
BBC News, Paris and Pau
On the face of it, the 35-hour week is here to stay. Like paid holidays and the welfare state, it is widely seen as an "acquis social" - one of those left-wing innovations that have become permanent fixtures of the French system.
Some French want the freedom to work longer hours
President Jacques Chirac left it in place in 2002 after inheriting it from the previous socialist administration.
His potential centre-right successor, Nicolas Sarkozy, has also pledged not to scrap the 35-hour-week if he wins Sunday's presidential election - only to make it more flexible.
But despite the apparent consensus, the days of "reduced working time" - as it is officially known - could be numbered.
A silent but powerful hostility has been growing for years, and whoever ends up running France may have to make wrenching changes.
Take the case of Alain Bie, 30, who has just started a job as a bartender in the south-western town of Pau.
"The owner told me that normally I was restricted to 35 hours a week, but I told him I wanted to be able to work more and make more money," he says.
At the other end of the country, Nicolas Duport, a 29-year-old jewellery worker from Paris with a wife and child to support, expresses the same concerns and says they will influence his vote on Sunday.
"If Sarkozy is elected we will be able to work an extra four hours," he says approvingly.
'Struck a chord'
Mr Sarkozy - whose main economic motto in the campaign plan has been "work more, earn more" - wants to encourage overtime by making it largely tax-exempt.
"This has struck a chord in the working class electorate," says Jean-Claude Casanova, editor of the political review Commentaire.
"Sarkozy has capitalised on the silent criticism of employees who want more money in their pockets."
The 35-hour week was thought up in the mid-1990s to revive the socialists' fortunes following an electoral meltdown.
The idea was to resolve France's entrenched unemployment problem by sharing out work, while at the same time indulging the nation's taste for fun and leisure.
Sarkozy's plans to alter the 35-hour week are popular with some
This was just a vague aspiration, but when the socialists unexpectedly won legislative elections in 1997 they had to find quickly a way to implement the idea.
Negotiations with both unions and employers led to a semi-flexible system - the 35 hours were treated as an annual average, and time worked in excess of this in any given week would be compensated by extra leave.
A decade on, the system is under attack.
Economists say employment is not a fixed quantity to be shared out.
The best way to create jobs, they say, is growth - and France has very little of either. It has the slowest growth of any large EU economy and unemployment remains high.
Given this sorry record, it is hardly surprising that no other country has adopted the 35-hour week.
France's European partners - notably Nordic countries - have moved in the opposite direction, making labour markets more flexible, and have seen their economies improve as a result.
Many ordinary people in France have noticed their country's relative decline and are talking like economists.
"We need deep reforms," says Claude Oudin, 49, a plumber from Paris. "Given our public debt, it is high time we did something. You must not prevent people from working more."
In some key branches of the French economy, a culture of hard work has been retained.
Royal wants to extend the 35-hour week to more companies
Restaurants are a case in point. "I do 12-hour days and working less would be unrealistic," says Laetitia Massoni, 30, a cook in a luxury hotel in the resort of Biarritz.
Employers who need a flexible workforce have to be creative. Many restaurants pay "overtime" (ie anything above 35 hours) without declaring it.
Other firms resort to temp work - a booming sector in France.
Millions temp because they cannot find permanent jobs, which are a rarity in a country where contracts must contain iron-clad guarantees.
But temping also suits many employees, like Ilyes Ouraghi, 30, a security guard from Pau.
"I work when I want and where I want," he says. "I would never go back to a permanent contract with a 35-hour week."
Most of those calling for deep employment reforms are likely to vote for Mr Sarkozy.
It may seem ironic that a member of an outgoing conservative government, should embody change, but a recent opinion survey published by Le Monde suggests this is the case.
His socialist rival, Segolene Royal, by contrast, is seen an a defender of the traditional welfare state. She has pledged to extend the 35-hour week to virtually all firms, through negotiation.
However few expect her to leave the system untouched if she is elected.
A newcomer, she has shown that she is not afraid to take on traditionalists in the socialist camp.
FRENCH ECONOMIC WOES
Slowest-growing large EU economy
Public debt 66% of GDP and growing
Her economic programme owes much to old-left ideas, but according to social analyst Louis Chauvel, she could be a force for reform.
"The Socialist Party is like a bank," he says. "You have a front office and the back office. Royal's kitchen cabinet is full of social democrats who admire the Nordic system."
Of course, fixing France's dysfunctional labour market will not be easy. Many French people still support the 35-hour week.
Last month, employees at a heavy goods factory in eastern France overwhelmingly reject a management offer to work more to allow the company to expand.
But scratch under the surface of such militancy and interesting nuances start to appear.
Mohammed, a cleaner from Pau, is dead set against Mr Sarkozy's plan to weaken the 35-hour week.
"Overtime would be decided by employers," he says. "Employees will be forced to work more. It would be terrible for older colleagues who want to spend time with their families."
But when asked about his own wishes, Mohammed's position is different.
"I'm a special case," he says. "I'm 23 and I'd like to work more."