Nurse Cécile Ngoue cannot stop and talk, she insists, or she will be late for her shift after attending a demonstration against reforms to working hours in French hospitals.

French health service workers like 52-year-old Ngoue have taken to the streets in recent days to protest against changes to the 35-hour working week, viewed outside France as totemic of the country’s rigid employment laws.

Ngoue, dressed in her uniform whites, stops all the same, and says: “We’re not lazy and we’re not opposing reform. We’re just asking for a little humanity in these changes. Everyone expects us to make sacrifices, but what about those higher up? We’re the wrong target, but the usual target. Like everyone else, we want time to rest and spend with our families. The problem isn’t the number of hours: it’s a lack of staff. We cannot work until we drop.”

Nothing divides France like the 35-hour week, or to give its correct name, the loi Aubry, after Martine Aubry, the Socialist minister who pushed it through in 2000 when she was part of a centre-left government “cohabiting” – sharing power – with a centre-right president.

When the centre-right controlled France between 2002 and 2012, it moaned about and tinkered with the 35-hour law, but did not repeal it. Easings and adjustments – what the French call détricotage, or unravelling – now mean companies can negotiate, for example, for working time to be calculated not weekly but annually – at just over 1,600 hours a year.

Les 35 heures has become the scapegoat for all the country’s economic woes. France’s neighbours regard the rule with a mix of scorn and envy, as evidence of supposed Gallic laziness. But that overlooks the fact that France’s hourly production figures are higher than Britain’s or Germany’s.

As the law has been loosened, companies have taken a flexible approach to the 35-hour week, paying overtime at higher rates, say. As a result, the “actual” hours worked have crept up: by 2012, state researchers found, the average number of hours worked by full-time staff in France was 39.5.At some companies, such as EDF, which is 85% state-owned, staff have it written into their contracts that they can claim between 27 and 31 days on top of the 27 days’ paid annual leave. A deal signed by EDF with staff in 1999, as the 35-hour working week came into effect, allowed some staff to work a 32-hour week. In a report in 2013 the French state auditors noted that the average number of hours worked by staff at EDF was 1,570 hours a year, well below the 1,607 hours a year expected of a full-time post according to the Code du travail. EDF is trying to buy out this privilege in return for longer hours.

President François Hollande and his socialist government, led by Manuel Valls, have repeated their commitment to les 35 heures.

But is France to be congratulated for creating work-life balance for its citizens, or criticised because it cannot afford such a luxury at the height of a global economic crisis? The arguments rage – and les 35 heures remain.

Martine Aubry, the architect of France’s working-time legislation. Photograph: François Lo Presti/AFP/Getty Images

Nobody denies France’s labour market has problems: stubbornly high unemployment; paltry growth; stifling and often incomprehensible set of employment laws (the latest edition reportedly runs to 3,689 pages); high social security charges; and complicated hire-and-fire rules that mean French employers prefer precarious short-term contracts over stable jobs.

However, Eric Heyer, a director at the Observatoire français des conjonctures économiques thinktank, says it is unfair for critics to fixate on the 35-hour law: “It’s not just false, but ridiculous to blame the 35-hour week for all France’s economic woes. If you look at the macroeconomics, there was no sudden drop in production or the economy following the introduction of the 35-hour week, and at the time France’s economy held out rather well. It’s not so great now, but that’s not the fault of the loi Aubry.”

The law was aimed at increasing employment: the thinking was that if weekly hours were reduced, companies would have to engage more staff. Economists still disagree on whether this actually happened.

Heyer cites official figures showing the law created 350,000 new jobs. This is far short of the hoped-for 2m new jobs vaunted by its supporters, he says, “but it’s not nothing”.

He added: “The 35-hour week was the subject of enormous negotiations at the time it was brought in. All those who negotiated and took part in the discussions benefited. It was a win-win situation for employers and employees. The employees saw their working time go down without a drop in pay, and companies introduced the principle of counting working time over a year.”

The changes that brought health workers on to the streets last week, it is worth noting, do not involve requiring staff put in more than 35 hours a week, but they would limit generous overtime payments (that mean the French health service now owes its staff €75m in unpaid hours), by introducing longer shifts, with more days off in between.

“It was not initially anticipated that the 35-hour week would be applied to hospitals,” Heyer said. “Hospitals are a regulated sector and couldn’t create new jobs. Besides, the number of new nurses is limited by the numbers coming out of medical schools, which is also regulated. Hospitals needed 5,000 new workers and found there were only 3,200 – so there’s a shortage.”

Heyer said: “The problem is that when someone is asked to work more than 35 hours – and they have the right to say no – the 36th hour and those after are paid at almost 25% more. This has created a huge bill. Obviously it needs rethinking.”

Even the Organisation for Economic Cooperation and Development, never knowingly overly left-leaning, does not have a particular problem with the 35-hour week.

Nicola Brandt, an OECD senior economist, told the Observer: “The problem with France’s labour market is a combination of factors. There are relatively high non-wage costs, including social contributions, and a high minimum wage. There’s high unemployment among older workers and young ones.

“We might argue about the methodology used to establish the benefits of a 35-hour week, but it didn’t make that much difference and it’s not the single biggest issue in the French employment market. In most cases, the employees and employers negotiate and adjust the law to suit their needs. If France went back to a 39- or 40-hour week, I’m not sure it would make much difference.”